There seems to be a lot of confusion about the use of antioxidants. Some swear by it and supplement companies seem to love it. Antioxidants are everywhere: in foods, in supplements, in skincare products, shampoos etc. They are often associated with health. On the other hand, there are reports that antioxidants can impair training adaptation. Recently I was in Keystone Colorado where one of the worlds experts, Professor Scott Powers from the University of Florida at Gainesville addressed exactly this issue. Although he acknowledging that there is still a lot we don’t know, he had a wonderful way of removing confusion. Here I will try to discuss his message (and I hope that I am doing your messages justice Scott!).

First, we need to understand what antioxidants are. Oxidation is the removal of electrons (The opposite of reductions which add electrons). We often think of antioxidants as things that scavenge free radicals. Free radicals are molecules that possess an unpaired electron in their outer orbital. They are highly reactive. There are also reactive species. These are molecules that promote oxidation (i.e. Oxidants) and these can be radicals or non-radicals. Anti-oxidants are molecules that prevent oxidation. The radicals are a highly reactive chemical species capable of damaging muscle fiber components such as proteins and lipids.

Because of the highly reactive nature of free radicals, they are very difficult to measure. They react very quickly and electrons move from one molecule to the next, making it almost impossible to measure them. We therefore measure some of the biomarkers of oxidative stress top get an indication. We measure lipids, protein or DNA that has been oxidized. The assumption is that the biomarker we measure is a reflection of oxidative stress, and this is not always the case.

Physical exercise increases the cellular production of reactive oxygen species (ROS) in muscle, liver, and other organs. In contrast to common belief, there is NO evidence that the source is increased mitochondrial production. Scott was quick to point out that the simplistic reasoning of exercise requires more oxygen, more oxidation at the site where oxidation takes place (mitochondria) cannot be backed by evidence. Originally, ROS were considered detrimental and thus as a likely cause of cell damage associated with exhaustion. This view is still portrayed a lot in the popular press. In the past decade, evidence showing that ROS act as signals that are important (amongst other functions) for training adaptation. ROS may thus be seen as positive not negative!

Of course excessive oxidation needs to be prevented and the body has several mechanisms for this. There are numerous enzymes in the body with an antioxidative capacity. These enzymes are the most important defence system.

Dr Powers pointed out that dietary antioxidants, when they get to the site of oxidation can be used as an antioxidant only once. They are used up and thus we need large amounts of exogenous antioxidants for these to be effective and these antioxidants must be at the specific site where oxidation is taking place. The antioxidant enzymes in our bodies can be used over and over again and these enzymes are upregulated (increase) with training. Many studies have shown thattraining increases the expression of classical antioxidant enzymes such as superoxide dismutase and glutathione peroxidase. So the more we exercise, the more enzymes we will make and the more protected we will be, independent of antioxidant intake.

Several studies have demonstrated now that high dose antioxidants are actually removing the signal for raining adaptation and the raining adaptations are impaired. Thus, the idea that antioxidant supplementation in exercise should always be recommended is incorrect.

Although the theoretical background may be sound, there is no scientific evidence to recommend increased quantities of antioxidants to physically active people, exceeding the amount provided by healthy balanced nutrition.

1. There is no evidence that physical training requires antioxidant supplementation above the normal antioxidants from a well-balanced diet.

2. Dietary supplementation of antioxidants can play a role when food intake is restricted or where a dietary deficiency of antioxidants is clinically determined (Rare!)

3. There is NO evidence that anti-oxidants have a positive effect on recovery

4. There is little or no evidence that anti-oxidants improve performance

5. There is emerging evidence that antioxidant supplementation in high doses can reduce training adaptation.

The practical implications are pretty straight forward

There is no need for antioxidant supplementation if you have a diet with varied fruits and vegetables, this is a sensible means of obtaining a balance of exogenous antioxidants. Studies have shown no advantages of antioxidant supplementation and high doses of antioxidants can be detrimental and should be avoided.

Further reading

Gomez-Cabrera, M.C., E. Domenech, M. Romagnoli, A. Arduini, C. Borras, F.V. Pallardo, J. Sastre, and J. Vina (2008). Oral administration of vitamin C decreases muscle mitochondrial

biogenesis and hampers training-induced adaptations in endurance performance. Am. J. Clin. Nutr. 87:142-149.

König D, Wagner KH, Elmadfa I, Berg A. Exercise and oxidative stress: significance of antioxidants with reference to inflammatory, muscular, and systemic stress. Exerc Immunol Rev. 7:108-33, 2001.

Powers, S.K., and M.J. Jackson (2008). Exercise-induced oxidative stress: cellular mechanisms and impact on muscle force production. Physiol. Rev. 88:1243-1276.

Powers, S.K., L.L. Ji, A.N. Kavazis, and M.J. Jackson (2011). Reactive oxygen species: impact on skeletal muscle. Compr. Physiol. 1:941-969.

In a previous blogwe discussed the effect of a simple mouth rinse with a carbohydrate solution on exercise performance. Carbohydrate mouth rinses have received quite a lot of attention (in fact this field seems to have exploded) and many studies have explored the effects of this mouth rinse on different modalities of exercise. However, it appears that the mouth rinse is most potent during exercise that is all out and lasts roughly one hour. The graph here focuses on that type of exercise. I have updated the graph from a previous article with a few new studies. The conclusion hasn't changed: there is a consistent effect of a mouth rinse on this type of performance. This effect is greater when the test is performed in the fasted state. The effects also seem exaggerated when tests are used that measure time to exhaustion rather than time trials.

Not all studies were included. I took the liberty to exclude 2 studies that had extremely low statistical power and therefore never had a chance of finding any effect (and indeed they did not find an effect). Power calculations should be part of an ethics application and low statistical power should also be picked up by reviewers! I may also have left out studies with positive effects.

Another interesting study is a study by Jensen et al that is in press at Medicine and Science ins Sprot and Exercise. This study showed improved time trial performance after 120 min of cycling. The authors reported significant changes in muscle recruitment and time over the last 20% of the TT, along with an average 1.7% improvement in TT time, suggest CHO mouth rinse helps maintain power output late in TT's compared to placebo.

References (newer studies)

James RM, Ritchie S, Rollo I, James LJ. No Dose Response Effect of Carbohydrate Mouth Rinse on Cycling Time-Trial Performance. Int J Sport Nutr Exerc Metab. 2017 Feb;27(1):25-31.

Jensen M, Klimstra M, Sporer B, Stellingwerff T. Effect of Carbohydrate Mouth Rinse on Performance after Prolonged Submaximal Cycling. Med Sci Sports Exerc. 2017 Dec.

Murray KO, Paris HL, Fly AD, Chapman RF, Mickleborough TD.

Carbohydrate Mouth Rinse Improves Cycling Time-Trial Performance without Altering Plasma Insulin Concentration. J Sports Sci Med. 2018 Mar 1;17(1):145-152.

The best choice of protein source for building muscle is, without question, a hot topic in Sport Nutrition. Sport scientists, dieticians and nutritionists alike are often posed the following two questions:

Do proteins from dairy, meat, and plant sources differ in their capacity to promote muscle growth during resistance exercise training?And if so, which is best?

Before we answer these questions let's discuss the best approach to tackling these questions.

A look inside the laboratory

The best science behind the most effective protein source for building muscle is based on data generated from carefully controlled and somewhat sophisticated laboratory studies. These studies usually involve strength-trained volunteers ingesting a single source of protein soon after a one-off weight-lifting workout. Simultaneously, skilled researchers apply what is called “stable isotopic tracer methodology”. This technique involves slowly pumping labelled (or “heavy”) isotopes consisting of synthetic amino acids directly into one forearm vein, serial blood sampling from the other and the collection of muscle biopsies, usually from the easily accessible vastus lateralis muscle. With access to specialized analytical instruments, not to mention technical expertise, this laboratory approach allows for the determination of muscle protein synthesis (MPS) — the “gold standard” for measuring the muscle building response to a given protein source.

What does the science tell us?

Animal sources of protein are often touted as more effective for muscle building than plant proteins. Consistent with this idea, laboratory studies have reported a greater post workout response of MPS when strength-trained young men consumed either skimmed milk or whey protein vs. a matched dose of soy protein [1, 2]. As further proof that animal proteins trump plant proteins, a study in middle-aged men revealed a greater stimulation of MPS at rest after ingesting a 100g (4 oz) lean beef steak vs. a soy protein marketed and sold as a bona-fide replacement for beef. Plus, in healthy older adults, ingesting 35 grams of micellar casein protein stimulated a greater MPS response compared with a matched dose of the cereal protein, wheat. So, what makes the dairy proteins and beef more potent than soy and wheat in terms of stimulating MPS? And is it all bad news for the vegetarian/vegan strength-based athlete?

As detailed in a previous blog, different protein sources are characterized by unique digestive properties and amino acid profiles. Most animal-based protein sources, including dairy, meat and eggs are more digestible than plant proteins such as soy, wheat, rice and potato. This means that a greater percentage of amino acids derived from animal protein sources successfully negotiate the small intestine and reach the circulation, rather than being extracted by the gut or taken up by the liver. As such, more amino acids (or building blocks) become available to the muscle for making new muscle protein, i.e. MPS, after ingesting most animal vs. plant protein sources.

As illustrated in the infographic above, plant and animal proteins also differ in terms of amino acid profile [3]. The essential amino acids (EAA), i.e. those amino acids that must be supplied by the diet, — in particular the amino acid, leucine — are key to driving MPS. In addition to providing a building block for making new muscle proteins, leucine itself acts as a signal to switch on the process of MPS. Crucially, as a general rule, the leucine content of animal proteins (8-13%) exceeds plant proteins (6-8%). The same applies for EAA content. In fact, whey, milk and casein are the only protein sources with a higher constituent EAA content compared with human muscle itself. Plus, animal proteins typically boast a complete profile of all 9 EAA’s, whereas plant proteins are deficient in at least 1 of the EAA’s, usually lysine or methionine. So, it seems clear that the superior response of MPS to ingesting dairy and beef proteins compared with soy and wheat proteins stems from inherent differences in digestive properties and amino acid profiles between proteins.

What next?

However, there are exceptions to these rules that, as such, offer hope for alternative plant-based proteins and therefore vegetarian strength-based athletes. For instance, the plant protein maize boasts a leucine content of 12% that exceeds most animal proteins. Plus, quinoa consists of an unusually high lysine (7%) and methionine (3%) content and therefore contains a full complement of all EAA. So, it may be that other plant proteins, in addition to soy and wheat, such as maize and quinoa are equally effective as so-called “higher quality” animal proteins from dairy or meat sources. Moving forward, as is so often the case in Sport Nutrition, much more work is needed before we as sport scientists can definitely state what protein source is best for muscle building in strength athletes.

Key points

Digestibility and amino acid composition are key factors that determine the potential of a protein source to stimulate MPS.As a general rule, the leucine content of animal proteins (8-13%) exceeds plant proteins (6-8%)Based on currently available evidence, animal proteins such as dairy and beef confer an advantage over plant proteins such as soy and wheat with regards to stimulating MPS post workout.The potency of alternative plant proteins such as maize, lentil, quinoa and pea for stimulating MPS post workout remains unknown.

References

1. Wilkinson SB, Tarnopolsky MA, Macdonald MJ, Macdonald JR, Armstrong D, Phillips SM. Consumption of fluid skim milk promotes greater muscle protein accretion after resistance exercise than does consumption of an isonitrogenous and isoenergetic soy-protein beverage. Am J Clin Nutr. 85:4:1031-40, 2007.

2. Tang JE1, Moore DR, Kujbida GW, Tarnopolsky MA, Phillips SM. Ingestion of whey hydrolysate, casein, or soy protein isolate: effects on mixed muscle protein synthesis at rest and following resistance exercise in young men. J Appl Physiol 107:3:987-92, 2009.

3. van Vliet S, Burd NA, van Loon LJ. The skeletal muscle anabolic response to plant- versus animal-based protein consumption. J Nutr. 145:9:1981-91, 2015

I have been helping athletes to create nutrition plans for their races for a long time. For 25 years, I have worked with, listened to and learned from professional as well as recreational athletes. My advice was always based on evidence, studies that we and others conducted in the laboratory and in the field. Many athletes I worked with solved their nutrition issues like stomach problems, running out of energy by having a solid nutrition plan based on science.

I was always asking the same questions and would work out a plan depending on the answers. When Bill Braun, an athlete himself, contacted me a little while ago, we started to develop a web based tool for endurance athletes that helps to create a personalized and evidence based nutrition plan.

We called the tool CORE as we believe that nutrition is at the CORE of every performance and performance starts from this CORE. The tool is now available online on www.fuelthecore.com. This blog describes the basics of what CORE does and some of the science behind it.

Why CORE?

Many endurance athletes don't get their nutrition right and therefore their races can be hit-and-miss. Often athletes quote nutrition as the main reason why a race did not go as planned? Why can’t they get it right? Maybe because there is so much information out there and so many opinions? Maybe because a plan that works for one person does not necessarily work for another? Nutrition is highly personal. Some athletes can tolerate anything, some athletes seem to get runners trots just from looking at gels! Some athletes sweat lots, some don't. Many factors will determine the requirements for a race including weather, temperature, humidity, of course the exercise intensity, the pace but also the availability of nutrition during a race and many other factors. There are a lot of things to consider. With CORE we tried to build a tool that takes all of this into account and for the athlete it will take the guesswork out of planning.

Under the bonnet

Without going into too much detail how the algorithms work, here are some of the factors that are taken into account:

Carbohydrate requirements

Carbohydrate requirements depend very much on the goal of training (or racing). If the goal is optimal performance, carbohydrate recommendations are generally higher. If training fat burning is a main goal, you want to minimise carbohydrate intake, so you don’t suppress fat burning. On the other hand, you don’t want the intensity of training to drop too much because that will mean, fewer calories burnt and less fat burnt! (these principles are discussed in this blog on periodised nutrition).

Fluid requirements

Sweat rate: there are individual differences and sweat rate is mostly influenced by the exercise intensity and environmental conditions. The amount of heat your body produces is determined by the power output. In other words, it is the pace that determines the heat production and not the perception of effort. If a professional cyclist and I both work hard at say 80% of our max. The pro cyclist may ride at 400W whilst I ride at 300W. This means heat production is roughly about 3200W for the pro cyclist and 2400W for me. So if an athlete tells us the expected time (pace) we have some idea of the absolute intensity.

We recommend to calculate sweat rates by measuring body weights before and after training in different conditions (check this blog on how to do this). If such measurements are not immediately available, predictions can be made based on the most important inputs that determine sweat rate.

5 step process

CORE is a 5 step process. Once you have gone through the first 2 steps CORE will know a little about you and your event. If the location of the event you are planning is known, the app will automatically retrieve the most accurate weather forecast at that time. There is enough information now to calculate some targets for carbohydrate and for fluids. The carbohydrate target is personalised, so that, if you don’t normally have a lot of carbohydrate in your diet and you don’t often train with carbohydrate, CORE would not recommend high carbohydrate intakes in a race (or training). The fluid target will allow a certain weight loss, as this is normal and to be expected, but it will make sure that this weight loss is not so much that it might affect performance.

Experienced athletes

If you are an experienced athlete who has experimented a lot in different races you can override the relatively conservative CORE advice and increase carbohydrate intake to levels above 60 grams per hour. You have to know that this is only recommended if the carbohydrate source consists of multiple transportable carbohydrates (read more here). So, although CORE can do it all for you, you can also work with your own targets using this tool.

Personalising

In step 3 you can select the products you want to use. These can be the products you are used to and you know you can tolerate. These can also be the products that are available on the course of a race. CORE has a number of races pre-programmed, which means that for those races not only does CORE already know what products will be offered on course, but also where on course what is being offered. So if you wanted to race and not bring any products, you simply plan with the available products on course. You make sure that you pick up those products from the feed stations.

CORE has well over 1000 products in the database. This includes many sports nutrition brands but also many normal foods such as fruits, home made rice cakes and so on. You can even select bacon, sandwiches and a complete smorgasbord if this is your personal preference!

Once you have selected water, a sports drink and another carbohydrate source, and you indicate your preferences for water versus sports drinks, CORE’s algorithms can do their job and generate a plan for you! You can than change and tweak this plan as much as you like. In fact, this tweaking is step 4. It is highly recommended that you move products exactly to where you want them. You can add products, remove products, or move product earlier or later. Every time you move something your totals will change, the dials will change and you may get closer or further away from your targets. Just keep an eye on the dials that will tell you whether your plan is on target.

Get a report

Once you are happy with your plan, you can get an overview of your plan (step 5: the final step). You will get more details of your plan and a simple summary of what you need to bring and what will be available on course. You can see your total sodium intake, your caffeine intake and so on. This reminds me that CORE does not recommend specific amounts of sodium or caffeine for individuals because large individual differences exist in the needs and these are probably best established by trial and error/personal experience. CORE will help you to calculate your totals for sodium and caffeine, so you can see of you hit your own targets.

In this final step you can also print a pace band or a summary plan many cyclists and triathletes have been using on their top tubes of their bikes to remind them of the plan during a race.

Pace bands and sticking to your plan

Your pace bands can remind you during a race or training to what you have planned. Now you have to execute your race or training and follow the plan. We recommend to stick to the plan as much as possible but of course use common sense. The biggest mistake (in my opinion) is to enter a race with no nutrition plan at all. The second biggest mistake, however, is to stick to a plan at all cost. Conditions may change and you still need to listen to your body.

This program will give a customised/personalized plan: no 2 plans will be the same because everyone is different and the conditions are always different. It will give you the best chances of a good race and aim to minimise any gastro-intestinal distress, preventing over as well as under hydration and keeping you fuelled to the finish.

Andre Greipel's bike ahead of Pari-Roubaix 2017, fitted with a CORE nutrition plan.

Cost

There is a free version of CORE which works fine but will not have all the features discussed here. The premium version of CORE is relatively inexpensive (a single plan $11.99 and unlimited use $99). Readers of mysportscience get 30% off by using coupon MYSPORTSCIENCE.

Most features here are included in the free version. But some of the features NOT included in the free version include:

- creating your own event

- access to all 1000+ products

- caffeine and sodium information

- setting your own targets for carbohydrate

I hope that you will like this project. I would love to hear any feedback, because we will continue to improve and make CORE bette,r so that more and more athletes can have great races and nail their nutrition plans, using science in a fully personalised way. Definitely check it out and let us know what you think! www.fuelthecore.com

Pacebands can help with pacing but remind runners of their nutrition plan details at the same time.

An often asked question is how much of what I eat can be used to build muscle? We can ingest a lot of protein and break it down, and digest it, but how much is used to build muscle?

Protein’s made up of 20 amino acids (AA) of which 11 are essential (EAA) so we need to eat enough protein to get the EAA. Digested proteins release AA into our circulation but not before the liver has taken its ‘share’ of the AA; and it’s pretty stingy, letting only ~30% of AA we ingest into the circulation. The branched-chain AA (BCAA) leucine, isoleucine, and valine are not used by the liver and are released for use by other tissues.

Leucine Leucine is the king AA, it turns on the anabolic signalling pathways and initiates muscle protein synthesis (MPS) by activating mTORC1 (full name: mechanistic target of rapamycin-complex 1) (see previous blog). Once leucine has ‘switched on’ muscle protein synthesis (MPS) then this process proceeds for a relatively short period of time (1-2h) until it is switched off. At some point you cannot stimulate MPS any further. So there is a finite amount of AA that are needed, in fact it may be that once leucine has activated MPS that even small quantities of protein are needed to support a continued MPS response.

Fate of amino acids So what are the fates of AA that enter muscle: use for MPS, transamination of N to form other amino acids (predominantly alanine and glutamine) with subsequent oxidation of the carbon-skeleton of some amino acids, and a small fraction of amino acids is used as TCA cycle intermediates. But the capacity for AA to stimulate MPS is limited and appears to ‘top out’ at around 0.25-0.4 g protein/kg bodyweight.

Why 0.25-0.4 g protein/kg bodyweight? Three studies form an evidence-basis for the value of 0.25-0.4 g protein/kg. Dose-response studies by Moore (1) and Witard (2) reached virtually the same conclusion as to the dose of protein that maximally stimulated MPS at ~0.25 g protein/kg regardless of whether the protein was isolated egg or whey protein, respectively. McNaughton (3) conducted a study that had two doses or protein and showed that MPS in their legs was 19% greater when young men ingested 40g of protein than 20g. However, the ‘added’ stimulation of MPS is small: 11% by Moore and 10% by Witard, and 19% by Macnaughton, respectively. This doesn’t really indicate that 40g is anywhere near twice as good as 20g in terms of MPS, but likely something like 15% better… not likely important in terms of lean mass gain.

Muscle protein breakdown

But what about muscle protein breakdown, isn’t that important? We don’t know what happens to MPB with increasingly large doses of protein? We do know that MPB is reduced by insulin which almost universally increases when we’re fed protein and/or carbohydrate and that it doesn’t take much insulin to maximally supress MPB. Kim (4) showed that larger doses of protein (70g versus 40g consumed as beef) supressed whole-body protein breakdown (WBPB) to a greater degree than a smaller dose. There are no data showing how well WBPB and MPB align and while muscle is part of WBPB it’s only ~20%.

So how much protein can your use to make protein?

I’d say between 0.25-0.4 g protein/kg/meal. The dose is likely to be higher when we’re eating real food, however. On this points, a meta-analysis from our lab showed that the hypertrophic response at protein intakes above ~1.6 g/kg/d was not associated with greater increases in lean mass. Thus, 1.6/4 meals per day = 0.4 g protein/kg/meal or 0.53 g protein/kg/meal if 3 meals were consumed. If you’re liberal on the estimate perhaps it’s as high as 2.2 g protein/kg/d? Now, you can eat, digest, and absorb more protein (a lot more), I don’t doubt that, but it doesn’t build muscle.

Key takeaways

AA from protein stimulate MPS in dose-response fashionMPS is maximally stimulated, when isolated high-quality proteins are consumed, at a dose of ~0.25-0.4 g protein/kg/mealLeucine is the critical AA that switched on MPSMPB is supressed with protein intake and the resultant insulinemia, but it appears that this occurs at low doses of protein/insulinAnalysis of available data suggests that at a daily intake of ~1.6 g protein/kg/d appears to be close to optimal for building muscleThe highest level of protein ingestion that may yield muscle building benefit is ~2.2 g protein/kg/dYou can ingest more protein than 2.2 g/kg/d, but it will not help build muscle

References

Moore DR, Robinson MJ, Fry JL, Tang JE, Glover EI, Wilkinson SB, Prior T, Tarnopolsky MA, Phillips SM. Ingested protein dose response of muscle and albumin protein synthesis after resistance exercise in young men. American Journal of Clinical Nutrition 2009;89(1):161-8. doi: 10.3945/ajcn.2008.26401.Witard OC, Jackman SR, Breen L, Smith K, Selby A, Tipton KD. Myofibrillar muscle protein synthesis rates subsequent to a meal in response to increasing doses of whey protein at rest and after resistance exercise. American Journal of Clinical Nutrition 2014;99(1):86-95.Macnaughton LS, Wardle SL, Witard OC, McGlory C, Hamilton DL, Jeromson S, Lawrence CE, Wallis GA, Tipton KD. The response of muscle protein synthesis following whole-body resistance exercise is greater following 40 g than 20 g of ingested whey protein. Physiol Rep 2016;4(15). doi: 10.14814/phy2.12893.Kim IY, Schutzler S, Schrader A, Spencer HJ, Azhar G, Ferrando AA, Wolfe RR. The anabolic response to a meal containing different amounts of protein is not limited by the maximal stimulation of protein synthesis in healthy young adults. American journal of physiology Endocrinology and metabolism 2016;310(1):E73-80. doi: 10.1152/ajpendo.00365.2015.

Master athletes (40 years and over) can attain similar levels of fatigue resistance, muscle mass, strength and power to younger individuals. This helps to delay the onset of many adverse health events associated with ‘normal’ ageing. Nonetheless, despite the impressively high level of performance in Master athletes, musculoskeletal deterioration remains somewhat inevitable with advancing age. Thus, nutritional considerations to enhance the speed of recovery, optimize training adaptations and, ultimately, improve or maintain athletic performance are likely to differ between Master athletes and younger athletes.

An overview of current protein recommendations for athletes

It is widely acknowledged that dietary protein has a range of important effect for athletes including alleviating exercise-induced muscle soreness and inflammation, stimulating the synthesis and accretion of muscle proteins, and potentiating muscle hypertrophy, strength and aerobic performance. The majority of the available evidence on the ergogenic effects of dietary protein has been generated from studies in younger athletes and very few involved older athletes.

The most current recommendations for protein nutritional support for strength/power range from 1.2-1.7g/kg/per day and are analogous to those for endurance athletes. Although markedly higher than the current Recommended Daily Allowance (RDA) of 0.8g/kg/day for protein, this alternative range should be thought of as an ‘optimal’ amount to support the increased demands of muscle repair, remodeling and adaptation of individuals engaging in exercise training. It is advised that this recommended daily protein amount is evenly distributed over 4-5 daily meals/snacks. A meal should aim to supply a protein dose of ~0.3-0.4g/kg in close proximity to training completion (i.e. in the 1-2 h post-exercise window) and every 3-4 hours across the day to maximize the stimulation of muscle protein synthesis (see also this guest blog by Professor Stuart Phillips).

The optimal source of dietary protein for athletic populations is the subject of much debate. It is generally considered that proteins that supply a full complement of essential amino acids, particularly leucine, offer the greatest advantage for stimulating muscle protein synthesis. In this regard, animal-derived proteins (i.e. whey, milk, beef) are often reported to promote superior muscle remodeling responses to plant-based proteins, although consuming a higher dose of plant-based protein, or combining various plant-based proteins together may provide an amino acid profile that is sufficient to optimize muscle remodeling.

Do protein nutritional needs differ for Master athletes?

Age-related muscle loss begins in fourth decade of life and is a harbinger for the loss of strength and onset of disability. To mitigate this age-related musculoskeletal deterioration, it is recommended that daily protein intakes should be ~1.2g/kg/day for older individuals (~50% increase above the current RDA). This position is, in part, based on evidence that protein ingestion to stimulate muscle protein synthesis requires greater relative intakes in older individuals. Thus, given the already elevated requirement for dietary protein to support muscle mass maintenance in older age, it is intuitive to expect that the protein nutritional requirement to support net muscle protein synthesis in the ageing athlete may be greater than younger athletes. Indeed, whilst post-exercise rates of muscle protein synthesis are saturated with ~20-25g of leucine-rich whey protein in younger individuals, exercised muscles of untrained older individuals are responsive to a higher 40g protein dose (2).

Therefore, a key consideration in defining protein nutritional requirements for Master athletes is whether these highly trained older individuals display a similarly impaired muscle anabolic response to dietary protein and exercise as their sedentary counterparts. To investigate this, Doering and colleagues (1) recently compared the rate of muscle recovery following a 30-minute downhill ‘damaging’ treadmill run in Master (53 years) and younger triathletes (27 years). Cycle time trial performance over 3 days of recovery tended to be lower in Master triathletes, and was accompanied by lower rates of muscle protein synthesis compared with the younger triathletes. Importantly, all triathletes consumed 20g of whey protein immediately after the downhill run followed by a diet containing ~1.6g/kg/day of protein (0.3g/kg/per meal) during the 3-day recovery phase, yet this was still insufficient to optimize muscle recovery in Master athletes. These data strongly suggest that Master athletes may require dietary protein intakes in excess of the current recommendations for younger athletes to support post-exercise muscle protein synthesis, recovery of performance and long-term training adaptations (suggested range: 1.6-2.0g/kg/day).

Refining this advice further, the requirement for higher dietary protein intakes in Master athletes may be particularly beneficial during training bouts/phases that cause damage to muscle contractile and connective tissue (i.e. lengthening contractions, intensified training, return from injury), as master athletes display a slower rate of recovery compared to younger athletes in such scenarios. Finally, very high protein intakes (≥2g/kg/day) may offer an additive benefit for musculoskeletal health and performance in the ‘oldest old’ Master athletes (i.e. those aged 80 years and over).

What can we take away from all this?

From what we know we can come up with some broad guidelines for the master athlete. Master athletes nearing 50 should probably start with higher per meal protein intakes (0.4g/kg, 4-5 times daily). This certainly won’t be harmful and can only be beneficial. For individuals who find that tough to achieve and want avoid supplements, an additional 1-2 servings of dairy with each meal (i.e. glass of fat-free milk and low-fat yogurt) or nuts/grains can be the difference. Pre-sleep protein (discussed here) is likely to be beneficial for Master athletes. It seems that Master athletes should aim for 40g of casein protein to maximize overnight synthesis rates, which is superior to 20g.

Depending on the event the athlete is training for, it may mean cutting other macronutrients (fat and/or carbohydrate) in main meals to accommodate the extra protein. Master strength/power athletes should aim to reduce fat and carbohydrate intake marginally to accommodate the extra protein in order to maximize their power-to-weight ratio.

References

Doering TM, Jenkins DG, Reaburn PR, Borges NR, Hohmann E, and Phillips SM. Lower Integrated Muscle Protein Synthesis in Masters Compared with Younger Athletes. Med Sci Sports Exerc 48: 1613-1618, 2016.Yang Y, Breen L, Burd NA, Hector AJ, Churchward-Venne TA, Josse AR, Tarnopolsky MA, and Phillips SM. Resistance exercise enhances myofibrillar protein synthesis with graded intakes of whey protein in older men. The British journal of nutrition 1-9, 2012.

Dr Leigh Breen is an Assistant Professor of Musculoskeletal Physiology and Metabolism in the School of Sport, Exercise and Rehabilitation

at the University of Birmingham. His research activity is conducted, primarily, under the auspices of the MRC-ARUK Centre for Musculoskeletal Ageing Research at UoB and centres on investigating mechanisms of age-related musculoskeletal deterioration and the development of exercise and nutritional countermeasures to this phenomenon.

When it comes to endurance events, the differences in performance between men and women becomes smaller and smaller, the longer the event. In fact, the last few years we have seen run splits for the women at Ironman Hawaii, that are at least as fast as the men’s! It is often hypothesised that this is because of differences in metabolism between men and women. It has been suggested that women are actually better at metabolising fat and can therefore sustain exercise for longer. Women would thus be better suited for very prolonged endurance exercise. This is an interesting theory, but are women really better at burning fat than men?

In the literature we find a number of studies comparing metabolism in men and women, but these studies are notoriously difficult to interpret because there are many ways you can make such comparisons.

The design of a study will have a major impact on the conclusions. For example, should we compare men and women exercising at the same absolute intensity (pace) or at the same relative intensity (effort). Should we compare fat metabolism expressed in grams per minute or should this be scaled to muscle mass? Women are generally lighter than men, so should be scale to body weight? Women also have a different body composition, so should we express our data per kg fat free mass (FFM)? And since fat oxidation changes with training how can we make sure that the men and women we compare, are trained in exactly the same way? These crucial study design questions have a major effect on the outcome of the studies and it is therefore perhaps not surprising that the conclusions have not been unanimous.

Although some studies report no differences between men and women, the majority of studies seems to conclude that fat oxidation is higher in women. We performed a study in 300 men and women (approximately 50:50) and measured fat oxidation over a wide range of intensities (1). Because we were interested in the intrinsic differences in the muscle in the ability to oxidize fat, we compared fat oxidation over a wide range of exercise intensities (from very low to high) in men and women. We expressed fat oxidation per kg fat free mass.

The results are shown in the infographic. Women were slightly better at oxidizing fat than men. Their peak fat oxidation was just over 10% higher and this happened at a higher exercise intensity. In other words, women had a right and upwards shift of the fat oxidation curve compared with men. This is the same change we would expect in a person who is better trained. So based on these findings we would have to conclude that women are better at burning fat than men, and might be more suitable for very prolonged endurance exercise where fat is the main fuel.

However, although this may be true, there are other considerations as well. In absolute terms men are actually better at burning fat because they have more muscle and higher energy expenditures.

The theory is that women would burn more fat and spare more of the small, but essential, carbohydrate stores. This would prevent "hitting the wall" in the last part of a race! Maybe this is true, but direct evidence is lacking.

Finally, it is important to note that the differences in the studies are actually quite small and maybe the practical relevance is not as significant as often suggested. For example, the difference in the figure here is 0.66 milligrams of fat per kilogram fat free mass per minute. For a 55kg (121 lbs) female athlete with 12% body fat this means that she would burn 42 mg more fat per minute than her male counterpart.

Per hour that would mean 2.5 grams! Or 22 kcal: the amount of energy we can find in 10 peanuts, one cup of sports drink, a quarter of a gel, a 5th of a banana or half an Oreo cookie? Would that make a difference? We will not know the answer until more research is done in female athletes!

Until then, it will remain fascinating to see how women and men battle for positions in the world’s longest endurance races!

References

Over the past few years branched-chain amino acid (BCAA) supplements have become very popular sports nutrition products. Proponents of BCAA supplements claim many benefits related to recovery from intense exercise. These claims range from enhanced muscle protein synthesis (MPS) and decreased muscle protein breakdown (MPB) to protection of the immune system, increased fat oxidation and decreased muscle soreness, among many others. The physiological rationale for these claims, let alone robust evidence from well-controlled human studies, is often weak, if not completely lacking. In the infographic above the European Food Safety Authority (EFSA) verdict is listed with each of the claims.

Probably the most common claim for the efficacy of BCAA supplementation is enhanced muscle growth with resistance exercise training. As regular readers of this site will know, the metabolic mechanism for muscle growth is net muscle protein balance. In other words: you are making more protein than you are breaking down. – in particular myofibrillar protein balance (the synthesis of contractile proteins). The balance between the rates of MPS and MPB over a given time period determine whether muscle mass is increased or decreased. BCAA consist of three essential amino acids, leucine, isoleucine and valine. BCAA not only provide building blocks for making new proteins, i.e. muscle protein synthesis (MPS), as do the all other amino acids, but act as stimulating compounds for the molecular anabolic pathways in muscle. There is evidence that BCAA are effective for stimulation of MPS and inhibition of MPB from cell and animal studies (since at least the 1970s). However, as we’ll see, the evidence for the efficacy of BCAA for muscle hypertrophy in humans is, at best, weak and, at least, equivocal – at least in healthy, young folk.

It is very clear, from studies in cells, animals and even in humans following exercise, that BCAA (leucine is by far the most important player here) stimulate the mTOR pathway, i.e. the molecular pathway that ‘turns on’ MPS. That is a very important function for BCAA. This stimulation is often cited as the rationale for recommending BCAA supplements to those interested in "getting huge". However, the stimulation of the mTOR pathway, in and of itself, is not the end-all-to-be-all for muscle growth. See an earlier blog on the limitations of relying on molecular data to make recommendations about nutrition. So, the question is, how effective is BCAA supplementation for stimulation of MPS so that muscle growth is enhanced? Unfortunately, despite the potential for BCAA to enhance muscle hypertrophy and the available evidence from cell and animal studies, there is a distinct lack of convincing data from studies in healthy, young weight lifters.

The problem with BCAA supplements alone, i.e. without the other essential amino acids, is that all of the necessary building blocks to make new proteins are not available for maximal stimulation of MPS. We recently demonstrated that post exercise MPS was increased with ingestion of BCAA(1), but the stimulation was only about half of that measured following ingestion of intact whey protein, i.e. all of the essential amino acids. The explanation for this result is that the BCAA stimulate the system, but that there are insufficient EAA to supply the substrate to sustain MPS. This notion is supported by studies from Prof Stu Phillips’ lab. Thus, it can be said that BCAA stimulate MPS following resistance exercise, but the response is much better with ingestion of an intact protein that provides all the EAA necessary to sustain maximal MPS.

In addition to stimulation of MPS, BCAA supplements are touted as ergogenic agents for a number of other reasons. One prominent rationale for use of BCAA supplements is to alleviate muscle damage. There is some evidence for this claim, including a study we published a few years ago (2) showing that BCAA supplementation reduced muscle soreness following damaging exercise. However, there was no discernible impact on muscle function in that study. So, with a relatively modest decrease in muscle soreness and no impact on muscle function, it is not clear how practically useful BCAA supplements would be for recovery from intense, damaging exercise. Moreover, other studies have not been able to demonstrate effectiveness of BCAA supplementation for reducing symptoms of muscle damage. So, at best we must consider the use of BCAA supplements to reduce muscle damage as equivocal.

In summary, overall, based on the available evidence, the best nutritional recommendation to optimize adaptations to training, including muscle hypertrophy and enhanced oxidative metabolism, would still be to eat sufficient high-quality protein (that naturally includes BCAA, of course) in the context of meals. At present, we do not believe there is sufficient evidence to recommend BCAA supplements for enhancing muscle anabolism or alleviating muscle damage or, for that matter, for any other reason.

References

2. Jackman SR, Witard OC, Jeukendrup AE, Tipton KD. Branched-chain amino acid ingestion can ameliorate soreness from eccentric exercise. Med Sci Sports Exerc. 42(5):962-70, 2010.

If you’re an athlete, you might consider caffeine in order to improve your performance – at least 75% of athletes do. The effects of caffeine are different from one person to another. You might have experienced this yourself; perhaps you can drink a cup of coffee just before bed, whilst your partner can’t sleep if they consume any caffeine after midday. Recently, researchers have suggested that these effects have a genetic component.

Why are the responses to caffeine so individual? Well, as you can no doubt imagine, the answer is complex. The impact of caffeine, both in our daily lives and during exercise, is governed by many different factors. One such factor is the speed by which caffeine is absorbed – for example, caffeine from caffeinated gum tends to be absorbed quicker than caffeine from a sports drink because it is absorbed through the lining of the mouth, as opposed to the stomach. The contents of your stomach can further slow caffeine absorption, with a full stomach reducing absorption rates. But even the same delivery of caffeine can give varying responses between individuals because caffeine breakdown (metabolism) by our bodies differs. This will affect how long caffeine can have its positive (or, if you can’t sleep, negative) effects for. Caffeine can also be more effective when the receptors that caffeine binds to are more abundant or more available.

\At present, variation in two genes, called CYP1A2 and ADORA2A has been shown to impact the performance enhancing effects of caffeine, although these early results have not been well replicated. These genes cause these effects through slightly different mechanisms. CYP1A2 creates an enzyme (called cytochrome P450) which is responsible for how our bodies break down caffeine, and a small change in this gene can predispose people to be “fast” or “slow” caffeine metabolisers.

If you’re a fast metabolizer, then you break down caffeine quicker, so the effects of caffeine should last for a shorter time – which sounds negative, but it may well be that the molecules caffeine is broken down into also improve performance, which means being a fast metaboliser could be useful. A study from 2012 found that fast metabolisers saw a greater performance enhancing effect of 6 mg/kg caffeine than slow metabolisers on a 40km cycle time-trial (1). Whilst these results have been replicated, other studies have shown no effect of this gene on performance enhancement following caffeine, so a definitive answer is not yet possible.

The second gene that may affect how much caffeine improves our performance is ADORA2A. This gene encodes for an adenosine receptor. When adenosine binds to this receptor it make us feel tired – not ideal for sport! One of the ways by which caffeine improves our performance is by competing with adenosine for the adenosine receptors. In other words the more caffeine that binds to these receptors, the less adenosine can. As a result, we feel less tired and lethargic. As such, variation in these adenosine receptors may alter have much caffeine improves our performance. A single study, from 2015, has examined this, finding that this gene did impact improvements in performance following caffeine use (2). Variation in this gene might also contribute to increased anxiety or poor sleep with increased caffeine intake, which could also affect sporting performance.

But genes aren’t everything, and differences in our environment (a collective term that refers to non-genetic factors) also contribute to the inter-individual response to caffeine use. These include smoking, vegetable intake, menstrual cycle stage, and training status. Differences in how the caffeine is consumed, such as dose, timing, source, all impact how much caffeine improves our performance. Interestingly, those that believe caffeine will enhance their performance see a greater performance enhancing effect during exercise than those who don’t (3).

It is therefore clear that a large number of factors impact how much caffeine improves our performance. These fit broadly into three categories; genetic, environmental (i.e. non-genetic) and epigenetic (changes in genetic expression that aren’t caused by changes to the underlying genetic code). This inter-individual variation is so clear and so well replicated - and yet we have very broad, standardized caffeine recommendations: 3-9 mg/kg, taken 60-minutes before. This means there is a mismatch between what we know – the response to caffeine is highly individualized – and what is often preached – a one-size-fits-all recommendation on how to use caffeine in sport.

What does this mean to you?

One day, we might be able to use genetic profiling to give us a better idea of how we might respond to caffeine. But in the meantime, it comes down to self-experimentation. If you use caffeine to improve your performance, experiment with different dosages and different timings. Try it in tablet form and as part of a drink. Monitor how it affects you – do you sleep well that night? Are you anxious? This constant self-experimentation and self-assessment carried out in training enables you to select the caffeine strategy best suited to you, as opposed to the current one-size-fits-all recommendations, which are aimed at the average person; and, as we all know, you’re not average.

References

Womack CJ, et al. J Int Soc Sports Nutr. 2012;9(1):7. Loy B, et al. Journal of Caffeine Research 2015;5(2):73-81.Pickering C, Kiely Are the Current Guidelines on Caffeine Use in Sport Optimal for Everyone? Inter-individual Variation in Caffeine Ergogenicity, and a Move Towards Personalised Sports NutritionJ. Sports Med. 2017 (In Press).

Athletes, particularly in endurance sport, implement various dietary practices such as a low residue diet or lactose elimination to reduce the risk of exercise-associated gastrointestinal (GI) distress. GI symptoms are multifactorial, transient, challenging to replicate and influenced by placebo effect, so the true efficiency of dietary strategies require tailoring to the individual. This is further complicated by the fact that an implemented plan may be successful one race and not for the next. Recently, a more novel dietary approach was tested in runners with persistent exercise-associated GI distress: a short-term low FODMAP diet (2).In this previous articles we explained what FODMAPs are.

Many athletes avoid foods high in FODMAPs, such as lactose or legumes, with the aim to reduce GI symptoms and there seems to be a high rate of perceived symptom improvement (4). Repeated stress placed on the gut combined with high carbohydrate intakes and high FODMAP loads present in many sports foods may create the perfect storm for FODMAPs exacerbating exercise-associated GI symptoms. Exercise stress is known to impair gut motility and permeability and epithelial injury and it is plausible that preexisting FODMAPs in the GI tract, such as the high fructan pasta meal eaten the night before a race, or ingested during strenuous exercise (e.g. dried dates and oats in energy bars) could increase osmotic load and colonic gas volume, whereby worsening symptoms. Connecting this clinical concept, a short-term (6-day) low FODMAP diet was tested in healthy runners with persistent moderate to severe exercise-associated GI symptoms to see if symptoms during running and daily (symptoms occurring outside of exercise but potentially influenced by exercise stress) could be reduced.

In a recent cross over study (1), recreationally competitive runners with self-reported GI symptoms were given both high (~41 g FODMAPs/day) or low FODMAP (~8 g FODMAPs /day) diets. The diets were similar with minor modifications of ingredients to achieve varying amounts of FODMAP content. Runners were told they were being given ‘specific carbohydrate diets’ with pre-made and frozen meals and snacks supplied. Interestingly, usual FODMAP intake was checked before the study and all participants ate a high FODMAP diet (~43 g FODMAPs/day), similar to the high FODMAP diet given in the study. During each intervention period the runners completed two hard runs: one 5 x 1000m interval, and a 7km threshold run (2).

On the low FODMAP diet 9 of 11 runners reported fewer and/or less severe GI symptoms daily throughout the study on the low-FODMAP diet. Incremental area under the curve (AUC), which is an overall measure of how much GI distress an individual experienced during each diet, also confirmed that symptoms were lower with the low FODMAP diet. Although, during exercise GI symptoms were not clearly different this might be distinguishable in future research that integrates harder and longer bouts of exercise.

Overall, this preliminary work suggests a low FODMAP approach may be promising tool to add to the practitioners’ toolbox for the treatment of exercise-associated GI syndrome. It is important to note that clinically healthy endurance athletes with exercise-associated GI syndrome do not instinctively require a low FODMAP diet. However, it may be a tool to reduce symptoms in certain individuals. If the plan is to follow low FODMAPs for a long time then it is advisable to determine the exact FODMAPs that are triggers (through FODMAP elimination and reintroduction), as it is unlikely that every food high in FODMAPs will amplify GI symptoms for all individuals. Athletes are encouraged to avoid unnecessary dietary restriction as a full low FODMAP diet can be quite restrictive. Moving forward, if a low FODMAP approach is being considered, work with an experienced practitioner to become properly educated and steer clear of the nonsense likely to be associated with the predicted food industry boom in the low FODMAP trend.

References

Costa RJS, Snipe RMJ, Kitic CM, Gibson PR. Systematic review: exercise-induced gastrointestinal syndrome-implications for health and intestinal disease. Aliment Pharmacol Ther. 2017;46(3):246-265.Staudacher, Irving PM, Lomer MC, Whelan K. Mechanisms and efficacy of dietary FODMAP restriction in IBS. Nat Rev Gastroenterol Hepatol. 2014;11(4):256-66.Lis D, Ahuja KD, Stellingwerff T, Kitic CM, Fell J. Food avoidance in athletes: FODMAP foods on the list. Appl Physiol Nutr Metab. 2016;41(9):1002-4.

Recently we have started hearing more about FODMAPs and FODMAP diets… Ask an Australian, and the term “FODMAP” is already well known. However, this term is just beginning to reach other parts of the world. The acronym FODMAP stands for fermentable oligosaccharide, disaccharide, monosaccharide and polyols. A mouthful so, lets stick to the acronym! Created by clinical researchers at Monash University (Melbourne, Australia), this unique diet was designed to treat irritable bowel syndrome (IBS). The success of FODMAP restriction and individualized FODMAP dietary guidance has proven to be a promising treatment to reduce GI symptoms in IBS patients; a condition estimated to effect up to 15% of the population.

Interestingly, symptoms of IBS are very similar in athletes who experience GI symptoms during or after exercise (1). Some symptoms common to both IBS and GI symptoms during exercise include bloating, diarrhea/loose stool, flatulence and abdominal pain. Emerging theory and evidence suggests that the use of low FODMAP diet or FODMAP restriction may be beneficial to reduce symptoms in athletes who struggle with persistent exercise-associated GI issues (2).

FODMAPs are a family of short chain carbohydrates that occur in a wide range of foods from onions to wheat-based breads. This family of poorly absorbed short-chain carbohydrates have been shown to increase osmotic load in the small intestine. This means that water will be drawn into the intestine and this can cause diarrhea. Upon transit to the colon FODMAPS are rapidly fermented (broken down) by colonic bacteria, creating gas. Mechanisms for FODMAPs potentially increasing symptoms in athletes are still being explored but many foods have been distinctly categorized as high or low FODMAP (At Monash University they developed a beautiful app that helps to find out which foods are high or low in FODMAPS, (Monash phone app). It is possible that FODMAPs ingested before or after strenuous endurance exercise could worsen exercise-related GI symptoms. This is still very new area of research and the athlete-specific mechanisms are not yet understood. Below are a list of high FODMAP foods that may be ingested frequently or in high quantities by athletes, particularly around or during competition.

It is still very early days to draw firm conclusions about the use of a low FODMAP approach to prevent exercise-associated GI problems. However, this diet may be promising tool for athletes struggling with GI distress. It is important to note that clinically healthy endurance athletes with exercise-associated GI problems do not instinctively require a low FODMAP diet and it can be very restrictive. If you are unnecessarily restricting your diet you may cause more problems than you are solving.

However, a simple change such as switching from a high FODMAP energy bar to a lower FODMAP alternative may be all that is required to reduce symptoms. High and low FODMAP foods, or the ones in between, can be challenging to navigate. If considering a low FODMAP diet it is advisable to work with an experienced practitioner and become properly educated. Continue reading here: Low FODMAP: A novel tool prevent GI problems?

References

1. Costa RJS, Snipe RMJ, Kitic CM, Gibson PR. Systematic review: exercise-induced gastrointestinal syndrome-implications for health and intestinal disease. Aliment Pharmacol Ther. 2017;46(3):246-265.

2. Lis DM, Stellingwerff T, Kitic CM, Fell JW, Ahuja KDK. Low FODMAP: A Preliminary Strategy to Reduce Gastrointestinal Distress in Athletes. Med Sci Sports Exerc. In press.

Carbohydrate improves performance during long events (>2h) (Read more). Fluid intake can help prevent severe dehydration and also contribute to performance. But is it best to drinks sports drinks, gels or bars, bananas or other sources of carbohydrate? In races athletes seem to make different choices and we see athletes compete with drinks only as well as athletes who consume a full smorgasbord! In order to address this question, we performed a number of studies at the University of Birmingham.

The studies were part of Beate Pfeiffer’s PhD studies. In the first study (1) she compared the intake of a sports drink with the intake of a gel containing the same amount of carbohydrate plus water. The cyclist rode for two hours at a moderate intensity and consumed 1 gels per hour (with a 2:1 glucose:fructose composition) with 200 ml of water or carbohydrate drink. In both trials the cyclists received the same amount of carbohydrate. The average carbohydrate intake was high: 1.8 g/min and fluid intake.

The carbohydrates were “labelled” with carbon 13 and this allowed Beate to calculate how much of the ingested carbohydrate was utilised during exercise. In the figure above the exogenous carbohydrate oxidation (how much of the ingested carbohydrate was used) is depicted for the two trials and it is clear that there was no physiological meaningful differences between the two forms of carbohydrate intake.

This is not surprising because in one case carbohydrate is mixed with water in a bottle, and in the other case, the carbohydrate gel is ingested and mixed with water in the stomach. The concentrations of carbohydrate are the same and that means that the delivery of carbohydrate is expected to be very similar.

The bottom line is that it doesn't matter whether the carbohydrate is delivered as a sports drink or as a gel with water. A note of warning: if the gel is consumed without the water, then the stomach contents will be highly concentrated and this will slow down the gastric emptying of the fluids and is also more likely to give gastrointestinal problems.

The second study (2) that was performed compared an energy bar with a carbohydrate drink. The design of the study was very similar: cyclist rode two hours again and this time they received a carbohydrate drink or an energy bar plus water. The total amount of carbohydrate ingested as well as the total amount of fluid ingested was matched in the two trials. The bar used in this study was a commonly available energy bar high in carbohydrates, but low in protein, fat and fibre. The results of this study are displayed in the figure below. Also here, the difference between the solid food plus water and the carbohydrate drink is small and not statistically significant. Carbohydrate use from the bar seemed slightly lower but the difference is small. It is very likely that this is because this particular bar had very low levels of fat, protein and fibre. A bar higher in fat, protein and fibre is likely to slow gastric emptying and will reduce the delivery of the carbohydrate.

What the results of these two studies tell us, is that the form in which carbohydrates ingested does not really matter for the oxidation of the carbohydrate. In other words as an athlete, you can mix and match and you can use gels, bars or a sports drink or whatever you prefer to get your carbohydrate. In terms of fluid delivery, which was not tested in this particular study, one would expect that with solid food fluid delivery is slightly impaired compared to liquid.

So athletes can mix-and-match and use whatever source fits best with their preferences. Some athletes will prefer to go fluid only, others really need to eat something to get through longer races. For some athletes gels are a convenient way to take carbohydrate, but not everyone is a fan of them. So choose whatever carbohydrate source works for you. Work out the target and plan your race nutrition accordingly!

References

1. Pfeiffer et al MSSE Med Sci Sports Exerc. 42(11):2030-7, 2010

2. Pfeiffer et al MSSE Med Sci Sports Exerc. 42(11):2030-7, 2010

Sleep is generally recognised as a critical factor in athlete’s performance. Sleep is thought to affect both physiological and cognitive function, that can affect sports performance. Recent evidence, suggests that athletes have lower quality of sleep as well as lower quantity of sleep, compared with the non-athlete, particularly during periods of intensified training (Read Sleep disturbances in trained athletes). Lack of sufficient sleep is likely to have detrimental effects on athletic performance.Compromised sleep might also influence cognition, learning, memory, pain perception, immunity and inflammation. Chronic partial sleep deprivation may result in changes in carbohydrate metabolism, protein synthesis, appetite, and food intake. These factors can ultimately have a negative influence on an athlete’s nutritional, metabolic and hormonal status and could therefore potentially reduce athletic performance.

A number of neurotransmitters (e.g. 5-HT, gamma-aminobutyric acid, orexin, melanin-concentrating hormone, norepinephrine, and histamine) have been associated with the sleep-wake cycle. There are some nutritional interventions that can influence these neurotransmitters in the brain and so may thus influence sleep. For example, carbohydrate, tryptophan, valerian, and melatonin and others have been investigated as possible sleep inducers and represent promising potential interventions to improve sleep quantity and/or quality.

Synthesis of 5-HT in the brain is dependent on the availability of its precursor, the amino acid tryptophan (Trp). Trp is transported across the blood–brain barrier by a transport system that is shared by a number of large neutral amino acids (LNAA) including the branched chain amino acids (BCAA) leucine, isoleucine and valine. Thus, the ratio of Trp/LNAA in the blood is crucial to the rate of transport of Trp into the brain. Ingestion of protein generally decreases the uptake of Trp into the brain, as Trp is the least abundant amino acid and therefore other LNAA are preferentially transported into the brain. The ingestion of carbohydrate, however, increases brain Trp as the rise in circulating insulin (as a result of the increase in blood glucose concentration) stimulates the uptake of LNAA into skeletal muscle, which results in an increase in free Trp in the circulation, an effect that promotes its uptake into the brain.

There have been numerous investigations of the effects of Trp supplementation on sleep (1), and it appears that Trp doses as low as 1 g can improve sleep latency (time before falling asleep) and subjective sleep quality.

Melatonin is a hormone that influences the sleep-wake cycle by inducing a sleep promoting effect. Light exposure of the retina of the eyes results in a suppression of melatonin secretion. Some nutritional interventions that increase Trp availability or reduce the plasma concentration of LNAA can increase melatonin production and promote sleep. This can be achieved by several means:

a high protein diet that contains more Trp than LNAAingestion of carbohydrate (This may increase the ratio of free Trp to LNAA and facilitate the release of insulin, which promotes the uptake of BCAA into the muscle)

Research investigating the use of melatonin for primary insomnia has demonstrated inconclusive results. A meta-analysis reported a reduction in sleep-onset latency of 7 min, and concluded that while melatonin appeared safe for short-term use, there was no evidence that melatonin was effective for most primary sleep disorders (2).

Another recently investigated nutritional supplement is tart cherry juice which contains relatively large amounts of phytochemicals including melatonin. The ingestion of tart cherry juice has been shown to increase urinary melatonin, and when consumed for a one week period was shown to result in modest improvements in sleep time and quality (3) compared with placebo.

Recent studies on the effects of carbohydrate ingestion on indices of sleep quality and quantity indicate that high carbohydrate meals consumed in the hour before bedtime improve sleep quality and reduce wakefulness. Solid compared with liquid meals tend to reduce sleep onset latency (time taken to fall asleep) up to 3 h after ingestion, and a high glycemic index (GI) meal significantly improves sleep-onset latency above that with a low GI meal if consumed 4 h (but not 1 h) before bedtime. A few studies have investigated more chronic manipulations of habitual dietary intake on sleep and these have suggested that diets higher in carbohydrate result in shorter sleep-onset latencies, diets higher in protein result in fewer wake episodes and diets high in fat may negatively influence total sleep time.

Valerian is a herb that binds to gamma-aminobutyric acid type A receptors and is thought to induce a calming effect by regulation of the nervous system. Results of a meta-analysis investigating the efficacy of valerian showed a subjective improvement in sleep quality (4). While valerian is one of the more common ingredients found in supplements claiming to promote sleep, side effects such as drowsiness, dizziness and allergic reactions can be observed.

Other suggested sleep aids have not been adequately investigated and are not supported by scientific evidence: passionflower, kava, St. John’s wort, lysine, glycine, magnesium, lavender, skullcap, lemon balm, magnolia bark, and nucleotides. Many of these can be found in supplements that are claimed to improve sleep quantity and/or quality.

Current practical recommendations to improve sleep via nutritional interventions include:

Diets high in carbohydrate may result in shorter sleep latencies.Diets high in protein may result in improved sleep quality.Diets high in fat may negatively influence total sleep time.When total caloric intake is decreased, sleep quality may be disturbed.The hormone melatonin and foods that have a high melatonin concentration (e.g. tart cherries) may decrease sleep onset time.Subjective sleep quality may be improved with the ingestion of the herb valerian

It is important to note though that the research in this area is limited and more work is needed before firm conclusions can be drawn.

References

1. Silber BY, Schmitt JA. Effects of tryptophan loading on human cognition, mood, and sleep. Neurosci Biobehav Rev. 34(3):387-407, 2010.

2. Buscemi N, Vandermeer B, Hooton N, Pandya R, Tjosvold L, Hartling L, Baker G, Klassen TP, Vohra S. The efficacy and safety of exogenous melatonin for primary sleep disorders. A meta-analysis. J Gen Intern Med. 20(12):1151-8, 2005.

3. Howatson G, Bell PG, Tallent J, Middleton B, McHugh MP, Ellis J. Effect of tart cherry juice (Prunus cerasus) on melatonin levels and enhanced sleep quality. Eur J Nutr. 51(8):909-16, 2012.

4. Fernández-San-Martín MI, Masa-Font R, Palacios-Soler L, Sancho-Gómez P, Calbó-Caldentey C, Flores-Mateo G. Effectiveness of Valerian on insomnia: a meta-analysis of randomized placebo-controlled trials. Sleep Med. 11(6):505-11, 2010.

A highly recommended overview is written by Shona Halson:

Often we see articles published in magazines with blazing titles telling us how science shows that we need to avoid certain foods or eat certain things. But we then read the complete opposite advice the week after! In sports science we have seen some great examples recently.

For example, we have seen headlines for ice baths. One day they are recommended the next day you need to avoid them! Or we see headlines for sugar, one day sugar seems bad (even toxic!) and the next day it is good. Or we are recommended to train with carbohydrate or without carbohydrate! Antioxidants are good and the next week bad!

How is this possible? Why are all these scientific studies contradicting each other?

In this articles I am trying to get to the bottom of this issue. Before we discuss this, we need to understand a little more about what science is and how it works. What is science?

One of the best and easiest to understand definitions that I have come across is this one by Astrophysicist Neil deGrasse Tyson:

“Do whatever it takes to avoid fooling yourself into thinking something is true that is not, or that something is not true that is”.

Science refers to a method where you make observations, and formulate a hypothesis about the truth. You then carefully design a study to test the hypothesis, and your data will either support the hypothesis or not. If it doesn’t, scientists admit that they may have been wrong and adjust their hypothesis and test the new hypothesis. Science distinguishes itself from all other branches of human pursuit (like religion) by its power to probe and understand the behaviour of nature on a level that allows us to predict with accuracy the outcomes of events in the natural world (1).

The outcomes of scientific studies will depend on many factors. In sport science for example, the outcomes will depend on the way the research is conducted (study design), the level of the athlete (world class or recreational), trained or untrained, the environmental conditions, the diet, the time of day of the measurement and many other factors. When two studies are compared, some of these factors are going to be different, so you are hardly ever comparing like for like. Conclusions of a study are therefore often highly specific to the conditions of the study. We then try to extrapolate these results to a wider population, but have to be very careful when we do this. For example, if we find something in a test tube, it does not mean the same thing also works in a living human. If we find something in a patients with a particular disease, it does not mean that we can extrapolate these results to elite endurance athletes! The conclusions of a good study will take this into account and be specific to the conditions.

It is usually not the studies that contradict each other, but the interpretation of the results! Popular press usually doesn’t have the patience to try and understand all these factors that could have influenced the results. And the conclusions directly from the scientific paper are not “reader friendly”: if it specifies too much that this is only found in these patients with a particular disease. It makes a much better headline to immediately extrapolate this to the elite endurance athlete and people will be reading the article!

This of course is a disservice to the reader as well as to the scientific process. Although we need to translate science into practical recommendations (and I have tried to do this my entire career), when we do this, we should never do it on the basis of just one study. We should look at all the studies, understand the “totality of evidence”, understand the shortcomings of certain studies and then make a decision on what the best advice would be. When we give the advice we still need to be specific who the advice is for!

For example, creatine may be a supplement that works, but it will work in very specific condition for individuals with very specific goals. But for other athletes, with different goals and in different conditions the results of creatine supplementation may actually be negative! We refer to this as the context, and usually advice without the context is poor or counterproductive!

So when reading articles, always be wary of conclusion based on one particular study. Ask yourself what other evidence is there to support, compliment or contradict this particular study. If an article tries to draw conclusions far beyond the study, that is very likely a problem. What you really want to know is: what does the totality of evidence tell us and how much can we really extrapolate the results?

Over time, science discovers objective truths. These are not established by someone who is seen as an authority, nor by any single research paper, no by anecdotes. The popular press, in an effort to break a story, may mislead the public’s awareness of how science works by headlining a just-published scientific paper as “the truth,” (1).

1. What Science Is — and How and Why It Works Neil deGrasse Tyson- The Huffington Post Nov 18, 2016

It is generally accepted that aerobic exercise capacity in hot conditions is reduced whilst sprint performance may even be improved (see previous blog). The impact of environmental temperature and humidity on endurance performance can be significant. Marathons are slower when the temperatures rise above 11oC and many Ironman competitions are held in very hot conditions. This article will discuss why performance is impaired in the heat.

Heat production is directly proportional to exercise intensity, so extremely strenuous exercise, even in a cool environment, can cause a substantial rise in body temperature. Humans are roughly 20% efficient, which means that for every 100 Watts we produce, we also produce 400 Watts of heat. Of course athletes who produce 400W would produce a whopping 1600Watts of heat! The body has various ways to remove this heat and sweating is often the most important one. Sweating will allow an athlete to remove heat but it may also result in dehydration, which eventually makes it more difficult to regulate body temperature. When the environment is hot and humid is becomes more difficult to remove this heat through conduction and convection and we have to rely solely on sweating.

Large increases in body temperature during exercise are unlikely to occur in individuals who run at a slower pace (e.g., those who run a marathon in 4 to 6 hours) but are common in the faster, highly motivated athletes (who are able to produce more power and thus more heat).

For a while it was thought that when body temperature rises to about 39.5 °C (103 °F), central fatigue (i.e., fatigue in the brain rather than in the working muscles) would develop (1). This was seen as a protective mechanism to prevent overheating. It was based on studies, where subject exercised in the heat till they were exhausted and always seemed to stop when core temperature reached about 39.5 °C (103 °F).

However, it has now become clear that an interplay of multiple factors and not just core temperature is responsible for performance decrements in the heat (Nybo et al. 2014) (Figure X).

It is now understood that heat per se affects performance but that hypo hydration makes things worse. If the body heats up and the body becomes dehydrated to a significant degree all physiological functions are likely to be compromised.

Cardiovascular

When becoming dehydrated plasma volume may be reduced, whilst blood vessels expand. This makes it harder to maintain blood pressure and blood flow, whilst heart rate is increased. If the cardiovascular system is compromised this may affect oxygen delivery and metabolite removal.

Central Nervous system

The brain will heat up and there are a number of changes in the brain like fuel depletion, changes in neurotransmitters , accumulation of ammonia, cytokines etc that may alter brain function.

Muscle

Heat also directly and indirectly influences muscle function, there is accumulation of metabolites and an increase rate of glycogen breakdown.

Respiration

Increases in ventilation and breathlessness are usually observed.

Psychological factors

Last but certainly not least, there is increased discomfort and effects on pain tolerance, mood, and motivation, all of which can influence performance.

So what causes decreased performance in the heat?

So, explaining why performance is decreased in the heat, predicting how much performance will be affected, and how much certain levels of dehydration will influence this, is complex. It is clear that there is not one factor but many factors that work together to cause fatigue (summarised in the figure and in (2). There is still much that is incompletely understood and Nybo et al (2) in an excellent review of the literature concluded that future studies have to try and isolate each of the factors that influence performance in the heat and study its importance. Obviously this is a time consuming and no easy task.

From a practical point of view: we cant usually change the environment, therefore it is recommended to minimise dehydration and look for opportunities to cool skin and body.

References

Dehydration, if severe enough can slow you down. Drinking can prevent this, but if you need to drink and how much depends on your sweat rate. Therefore, it is useful to know how much you sweat and this will be very different for each individual in a particular situation. In the literature we have recently seen a few great publications on sweat rates in different athletes. Some athletes may sweat up to 3 liters per hour in hot conditions!

Very few athletes know how much they sweat but it is actually very easy to calculate! This article will guide you through that process. The most important factors that determine how much you sweat are:

How much power you produce or how fast your run.The temperature and humidity as well as coolingThe clothes you wearYour level of acclimation and your training status (better trained and more acclimated will allow you to sweat more and regulate your body temperature better)Your genetic make-up (some people sweat more than others)

It is important to realize that you probably need to do several measurements in different conditions to get a good idea of your sweat rate: easy training and hard training, hot conditions and cool conditions and so forth. The more you measure the better you will be able to predict your sweat rates.

Here is a brief step by step guide on how to figure out your sweat rate. Use the overview at the top of this page to do your calculations. White boxes are for values you measure and grey boxes for values you calculate.

1. Empty your bladder and record your weight (ideally nude body weight) (A)

2. Perform your workout, race or competition and record/memorize exactly how much you drank. This is easy if you drink from a bottle. You can weigh your bottle before (X) and after (Y) and record the difference (1 gram = 1 milliliter). (Z)

If you use different measurement units (fl oz) you need to convert all values to liters. Make sure all units are in kg or liters.

3. After exercise: Towel dry, empty your bladder and then record your weight (nude). (B)

4. Ideally, measure total urine production (U) after pre-weight recording. If that is not possible estimate it by using 0.3L per visit to the loo.

5. Now subtract your post-exercise weight from your pre-exercise weight to get the weight you lost during exercise.

6. Also subtract the weight of the bottle or bottles before (X) and after (Y) to obtain the volume you consumed (Z).

Weight lost C = A-B

Volume consumed = X-Y

7. You can now calculate your sweat rate: (C+Z-U) / time (in hours, calculated as number of minutes divided by 60).

A = weight before (kg)

B = Weight after (kg)

C = Weight loss (kg)

X = Weight of bottle(s) before (full bottles)

Y = Weight of bottle(s) after

Z = Weigh difference before and after

U = urine list

Your sweat rate estimations will never be 100% accurate, but they will give you a much better idea how much to drink than simply relying on thirst.

With the above calculation you make an assumption that all weight lost if sweat loss. This is not entirely correct. It is important to realize that here are other reasons for weight loss as well (you will use some carbohydrate and fat (up to around 1 lbs or 0.5kg during exercise of 2 hours or longer). During very prolonged exercise these losses may even be even greater.

Therefore, a small percentage weight loss 2-3% (1.5-2 kg for most athletes) is not a problem, but knowing how much you need to replace helps to prevent larger weight losses as a result of dehydration. Those larger losses can impact performance, especially in hot conditions. Knowing your sweat rate will also prevent you from overdrinking because you will know that there is no need to drink more than you sweat.

Knowing your sweat rate gives you important insights into how your body works and how different it will be in different conditions. Not everyone has access to laboratory facilities but this is something that is easily done at home with very simple equipment. Perform these measurements in different conditions and you will start to see trends and start to be able to predict your sweat rate!

References

Baker LB. Sweating Rate and Sweat Sodium Concentration in Athletes: A Review of Methodology and Intra/Interindividual Variability. Sports Med. 47(Suppl 1):111-128, 2017.

Gonzalez et al. Expanded prediction equations of human sweat loss and water needs. J Appl Physiol 107(2):379-88, 2009.

Thinking of getting a tattoo? An interesting recent study suggests, that came to my attention at the American College of Sports Medicine meeting in Denver, suggested that athletes may need to think twice before getting a tattoo... Tattoos have increased in popularity in recent times and it seems that especially in sport tattoos are prevalent. One anecdotal report indicated that 53% of all NBA basketball players during the 2015 to 2016 season were tattooed and that for two NBA teams, the Cleveland Cavaliers and the Houston Rockets, these numbers were as high as 3 out of every 4 players.

The tattooing process involves puncturing the skin with needles that contain a dye that is released and deposited 3-5 mm below the skin surface into the dermal layer. This dermal layer also contains sweat glands which are responsible for secreting fluids and play an important role in thermoregulation. It is therefore reasonable to question whether the tattoos interfere with a normal sweat response. A recent study investigated exactly this question (1).

The investigators recruited 10 individuals with tattoos on one side of their body. They measured sweat rate and sweat composition (sodium) in an area that was tattooed and they did the same on the other side of the body without a tattoo. The results clearly showed a lower sweat rate (53% lower) and a higher sweat sodium concentration (64%) from tattooed versus non-tattooed skin. This suggests that not only sweat rate is compromised but also that sodium re-absorption is impaired. So it appears that tattoos interfere with a normal sweating response. The authors also commented that these effects were not related to the age of the tattoo.

So what is the practical relevance? Should athletes avoid tattoos to maintain their ability to thermoregulate? It is probably too early to draw that conclusion and the answer is very likely: "it depends". It is likely to depend on how much skin has been covered with tattoos. For now, it is probably good for everyone, who is thinking of getting tattoos that will cover large parts of the body, to realise that this may have an impact on thermoregulation and potentially performance, especially in hot conditions.

References

1. Luetkemeier et al Med Sci Sports Exerc 49(7): 1432-1436, 2017.

A very popular believe in sports is that in order to get maximum effect of caffeine in competition you need to withdraw from caffeine in the days or even weeks leading up to it. The theory is quite attractive, because it seems to make sense that some caffeine habituation will take place. It is believed that non coffee drinkers or those that drink very little coffee will benefit more from caffeine. However, a study in the Journal of Applied Physiology appeared recently that seems to dispel this myth (1).

The study performed at the University of São Paulo in Brazil used a double-blind, crossover, counterbalanced design. Forty male endurance-trained cyclists were allocated into groups according to their daily caffeine intake:

Low (58 ± 29 mg/d or approximately 1 small cup of coffee), moderate (143 ± 25 mg/d or roughly 2-3 cups of coffee), and high consumers (351 ± 139 mg/d or roughly 5 cups of coffee per day). Participants performed 3 time trials (lasting approximately 30min) each before which they ingested a moderate dose of caffeine (CAF: 6 mg/kg body weight), placebo (PLA), or no supplement (CON). Caffeine and placebo were administered in capsules and ingested 1h before the start of the time trial.

Caffeine supplementation improved exercise performance by 3.3% compared to CON and 2.4% compared to PLA. These data are comparable with other caffeine studies. More importantly, performance benefits with acute caffeine supplementation during a ~30 min cycling time trial were not different between the groups with low, medium or high habitual caffeine intake. In other words: caffeine worked equally for everyone, low users, medium users as well as high users.

It is always important to discuss single studies in the context of the existing evidence, because one study does not necessarily mean that our views should change. Recently there was a well performed study (2) that suggested that 4 weeks of caffeine supplementation diminished performance benefits of acute caffeine supplementation in low habitual caffeine consumers (< 42 75 mg/d). However, giving low habitual users caffeine for 4 weeks, may be quite different from a habitual, high intake. The study can also not exclude the possibility that high habitual users can still benefit from caffeine. Finally, it does also not mean that refraining from caffeine products will increase the effects of caffeine.

Athletes are often encouraged to refrain from caffeinated products for up to 4 days before supplementing with caffeine to enhance the efficacy of acute supplementation. Despite this, a study by Irwin, et al (3). showed similar improvements in exercise with caffeine in habitual consumers regardless of a 4 day withdrawal period. Another study by Van Soeren, et al. (4) (the first study that directly addressed this question) showed equal exercise improvements with acute caffeine supplementation in habituated consumers after no, 2-days and 4-days of caffeine withdrawal. In a study we performed many years ago, I remember the observation that the largest performance improvements with caffeine were actually observed in the athletes with the higher caffeine intakes. We did not publish those findings because the number of subjects was probably too small to make firm statements, but the observation is interesting nonetheless.

Thus, it is fair to conclude that the balance of evidence suggests that caffeine withdrawal to get a better effect of caffeine is a myth. The recommendation from us is therefore to maintain your normal caffeine consumption during the preparation for your competition. You will still be able to benefit from the effects of caffeine in competition, and you will avoid any possible withdrawal symptoms in the days before.

References

L. de Souza Gonçalves, V. de Salles Painelli, G. Yamaguchi, L. Farias de Oliveira, B. Saunders, R. Pires da Silva, E. Maciel, G.G. Artioli, H. Roschel, B. Gualano. Dispelling the myth that habitual caffeine consumption influences the performance response to acute caffeine supplementation. Journal of Applied Physiology, in press.Beaumont R, Cordery P, Funnell M, Mears S, James L, and Watson P. Chronic ingestion of a low dose of caffeine induces tolerance to the performance benefits of caffeine. Journal of Sports Sciences 1-8, 2016.Irwin C, Desbrow B, Ellis A, O'Keeffe B, Grant G, and Leveritt M. Caffeine withdrawal and high-intensity endurance cycling performance. Journal of Sports Sciences 29: 509-515, 2011.Van Soeren MH, and Graham TE. Effect of caffeine on metabolism, exercise endurance, and catecholamine responses after withdrawal. Journal of Applied Physiology 85: 1493-1501, 1998.

Studies have convincingly shown that carbohydrate delivery during prolonged exercise can help performance. It is also clear that it is an advantage to absorb more carbohydrate and leave less unabsorbed carbohydrate in the intestine. This has two advantages: 1. carbohydrate accumulating in the gut might cause gastro-intestinal problems and thus this risk would be reduced. 2. delivering more carbohydrate may mean that performance improves more. There are several lines of evidence for this:

First, a meta-analysis of the literature showed a dose-response relationship. Secondly, at least 2 carefully conducted experiments demonstrate a dose response relationship between carbohydrate intake and performance. Thirdly, studies with multiple transportable carbohydrates, ingested at high rates, show that an increased delivery and oxidation of carbohydrates is associated with improved performance. Furthermore, there is evidence from events like Ironman Hawaii that higher intake is correlated with faster times (read: Is more carbohydrate better? And how much is too much?).

It has also been shown that the main barrier to better carbohydrate delivery is absorption. From this, we can conclude that anything that improves carbohydrate absorption could potentially improve performance in endurance events. This is where caffeine may come in.

Many years ago I was intrigued by a study that suggested that caffeine could improve intestinal absorption of carbohydrates (1). The study used markers of intestinal integrity and suggested that caffeine improved carbohydrate absorption. We then designed a study to test this hypothesis. Cyclists rode for 2 hours at a moderate intensity on 3 occasions. They received water on one occasion, and glucose or glucose plus caffeine on the other occasions. The amount of carbohydrate ingested was a moderate amount (48 g/h) and the amount of caffeine was a very high dose (5 mg/kg per hour) (to read how much caffeine is in coffee, see How much caffeine is in coffee?). We observed a remarkable increase in carbohydrate use from the drink, suggesting that more carbohydrate was absorbed! The only problem? The dose of caffeine was so high (10 mg/kg in total) that it may not easily translate into practical application.

Therefore, we designed a second study. Dr Carl Hulston was the first author. Again, cyclists performed 3 rides: water, glucose and glucose plus caffeine. The amount of carbohydrate ingested was similar to the previous study but the amount of caffeine was about half. The cyclists rode 1:45h at a moderate intensity, followed by a time trial, so we could also measure the effects on performance. This time, we did not find any effect on carbohydrate use from the drink and thus caffeine did not seem to have increased absorption.

The studies may seem somewhat conflicting, but it is possible that a high caffeine dose is needed to see the effects on carbohydrate use. The second study did, however, show effects on performance with added caffeine. It improved time trial performance by 9% compared with water and more than 4% compared with glucose only.In other words: glucose improved performance but caffeine plus glucose improved performance even more.

So where does this leave us? It seems that in order to see the effects of caffeine on carbohydrate absorption, a large dose of caffeine is needed. Such high intakes are not recommended because of increased side effects. The lower dose is effective in improving performance but it does not seem to do so by enhancing carbohydrate use. With highly individual responses to caffeine, the recommendation is that athletes experiment with lower doses and work out what works best for them.

References

Van Nieuwenhoven MA, Brummer RM, Brouns F. Gastrointestinal function during exercise: comparison of water, sports drink, and sports drink with caffeine. J Appl Physiol 89(3):1079-85, 2000.Yeo SE, Jentjens RL, Wallis GA, Jeukendrup AE. Caffeine increases exogenous carbohydrate oxidation during exercise. J Appl Physiol 99(3):844-50, 2005.Hulston CJ, Jeukendrup AE. Substrate metabolism and exercise performance with caffeine and carbohydrate intake. Med Sci Sports Exerc. 40(12):2096-104, 2008.

Read also:

Timing of caffeine intake in long races http://bit.ly/2au3W98

The capacity of the intestine to absorb carbohydrate is dependent on carbohydrate intake in the diet (for complete discussion read the recent reviewI wrote in Sports Medicine (1)). Similarly, the capacity to absorb is dependent on fat in the diet. If carbohydrate intake is increased, the capacity to absorb carbohydrate is increased. These adaptations can be very specific. For example, if glucose is increased the capacity to absorb glucose is increase, but the capacity to absorb fructose is unaltered. If the fructose content of the diet is increased the absorptive capacity for fructose is increased, but not glucose. Similarly with fat: If fat content of the diet is increased the capacity to absorb fat is increased without affecting the capacity to absorb carbohydrate.

These are interesting findings for athletes, especially because it has been demonstrated that absorption is the limiting factor for carbohydrate use from exogenous sources (ingested carbohydrate).

Glucose is absorbed through a protein that facilitates the transport across the cell wall of the intestine. This protein is called SGLT1: the sodium dependent glucose transporter 1. When the glucose content of the diet is increased for several days, the number of these transporters increases and the absorption of glucose increases in parallel. Fructose is transported by GLUT5 and something similar may happen to GLUT5 transporters.

Implications

If carbohydrate intake is reduced the opposite will happen. The number of transporters decreases and les glucose will be absorbed. Thus, any athlete who reduces dietary carbohydrate intake consistently will have a lower capacity to absorb glucose. When this same athlete now enters an endurance event and wants to use carbohydrate in the form of drinks, gels or energy bars, the absorption of the carbohydrate could be poor. This, in turn, could result in increased stomach fullness, bloating and increased gastro-intestinal problems.

This theory seems to be backed up by anecdotal evidence. Athletes who are carbohydrate restricting or athletes with very low energy intake often report more gastro-intestinal problems during events, especially when using these carbohydrate containing products.

Although there is merit in increasing the capacity to oxidise fat by sometimes training with low carbohydrate availability, having a low carbohydrate intake every day is not advised. It is more likely that the combination of low carbohydrate intake on some days, and high carbohydrate intakes might promote adaptations of fat metabolism as well as adaptations to carbohydrate metabolism and absorption. Improving the absorptive capacity of the gut is one of several methods we have available to train the gut. Read more here about training the gut for athletes.

So the periodised approach will help to increase fat oxidation, whilst maintaining the capacity to absorb carbohydrate. This means that on race day, one may burn more fat, spare some carbohydrate and deliver additional carbohydrate without causing gastro-intestinal problems.

References

These papers are available to download for FREE:

Related:

I remember that many years ago a review paper was published with the title: Is the gut an athletic organ? It hinted to the fact that athletic performance is very dependent on fuel and fuel delivery is dependent on gut function. Could the gut therefore be a much underestimated organ for athletes? In professional cycling it is sometimes said that a stage race is as much an eating competition as it is a bike race. From marathons and triathlons in particular, we know that fuelling during a race can be problematic as it is not easy to eat and drink whilst pushing the pace in these events. It is very common that athletes report stomach problems in attempt to do so. So the options are fuel less and have a chance of running out of energy and become dehydrated or fuel more and have a chance of getting an upset stomach. The optimal approach is of course somewhere in the middle where you balance intake with stomach comfort. However, there is one other approach that may work. The gut is an extremely adaptable organ and can be “trained” in a similar way to the way we train the muscle.

In a recent review in Sports Medicine I discuss the evidence that the gut can be trained. A lot of this evidence comes from studies in animals. But the evidence is strong and the few human studies we have point in the same direction. Contestants in eating competitions are known to ‘‘train’’ their stomach to hold larger volumes of food with less discomfort and— through regular training—are able to eat volumes of food within a small time window that are unthinkable for the average and untrained person. The current all-time record is 69 hot dogs (with bun) in 10 min. To achieve this, competitive eaters train using a variety of methods: chewing large pieces of chewing gum for longer periods of time or stomach extension by drinking fluids or by eating the competition foods. Volumes are progressively increased, and it takes many weeks to reach a level where these eaters can be competitive.

This demonstrates the adaptability of the stomach. Conducting this ‘‘stomach training’’ has two main effects: (1) the stomach can extend and contain more food and (2) a full stomach is better tolerated and is not perceived as so full. Both aspects could be beneficial in an exercise situation.

Another example relates to intestinal absorption: carbohydrate absorption during exercise seems limited to about 60 grams per hour (at least when a single type of carbohydrate, for example glucose, is ingested). An intake much above 60 grams per hour will most likely result in accumulation of carbohydrate in the intestine. However, increasing daily carbohydrate intake, mostly by increasing intake during the activity, has been shown to increase the absorption and oxidation of ingested carbohydrate (2). Read also this blog on increasing intestinal absorption.

The duration of this adaptation is unknown but in animal studies significant changes can be observed after a change of diet for only 3 days. The human study referred to above (2) used 28 days. From a practical point of view, I have been recommending 5-10 weeks at least once a week (Please note that in the absence of concrete evidence this is a best guess based on information that is available). It may be best to pick one longer training session per week, or the training that is closest to the race the athlete is preparing for and use this to practice the race nutrition intake.

There are a number of methods available to prepare the gut for competition. These are summarised in the figure below:

References

This paper is available to download for FREE:

1. Jeukendrup AE. Training the gut for athletes. Sports Medicine.

2. Cox GR, Clark SA, Amanda J. Cox AJ, Halson SL, Hargreaves M, Hawley JA, Jeacocke N, Snow RJ, Yeo WK, Burke LM. Daily training with high carbohydrate availability increases exogenous carbohydrate oxidation during endurance cycling. Journal of Applied Physiology Published 1 July 2010 Vol. 109 no. 1, 126-134 DOI: 10.1152/japplphysiol.00950.2009

Related

Nutrition can have a major impact on the adaptations to training (1). For example, in order to improve performance of the muscle, it is essential to exercise/train the muscle, but the effects of training influenced by nutrition. Nutrition can both improve and reduce the adaptations and is thus an important tool to optimize performance effects. It is not just the muscle that is affected (although this is the organ that is perhaps studied the most), other tissues such as the brain, the vasculature and the intestine, can also be affected.

There is more and more discussion, both in the scientific literature and also in the popular press, about the effects of nutrition on training adaptations. Sometimes this is referred to as “periodized nutrition”, sometimes “nutritional training” and others have referred to some aspects of this as “fueling for the work required” (2).

No one clearly defined, however, what methods are part of this periodized nutrition approach and people have interpreted the terms in different ways.

This is what I tried to address in a recently published review in Sports Medicine. I defined the concept of periodized nutrition as: the strategic combined use of exercise training and nutrition, or nutrition only, with the overall aim to obtain adaptations that support exercise performance. This is a mouthful, but it stresses that nutrition with or without exercise can affect the body in ways that will ultimately affect performance. It is not just the muscle, and performance is always the key outcome, even though the effects may not be acute and may only become visible after many weeks. The other important part of the definition is that is purposeful and planned! The term “nutritional training” is sometimes used to describe the same methods and these terms can be used interchangeably.

Some people think of periodized nutrition in terms of having different energy needs and intakes in different phases of the year. In some sports, carbohydrate intake may be much higher during the season and lower pre-season when changes in body composition may be the main goals. This is an example of periodized nutrition. Within a week there may be days with hard training and high carbohydrate intakes and days with low carbohydrate intake. Some will think of periodized nutrition as the strategic use of “training low” and “training high”: training with low and high carbohydrate availability respectively. But there is more. In addition to “train-low” and “train-high”, methods have been developed to “train the gut”, train hypohydrated (to reduce the negative effects of dehydration), and train with various supplements that may increase the training adaptations longer term.

The figure above shows a number of tools available to the nutritionist and trainer to optimize training adaptations. Which of these methods should be used depends on the specific goals of the individual and there is no method (or diet) that will address all needs of an individual in all situations. Therefore, appropriate practical application lies in the optimal combination of different nutritional training methods.

Some of these methods have already found their way into training practices of athletes, even though evidence for its efficacy is sometimes scares at best. Many pragmatic questions remain unanswered. One thing is clear however, in elite sport especially, the future of sports nutrition requires a close collaboration between trainer and sports dietitian/nutritionist. Working in silos will not work with the periodized nutrition approach and it is essential to incorporate nutrition planning into the long term (as well as short term) training planning.

References:

Free download of the paper in Sports Medicine:

2. Impey SG, Hammond KM, Shepherd SO, Sharples AP, Stewart C, Limb M, Smith K, Philp A, Jeromson S, Hamilton DL, Close GL & Morton JP (2016) Fuel for the work required: A practical approach to amalgamating train-low paradigms for endurance athletes, Physiological Reports, 4 (10), Art. No.: e12803.

More than 70% of visits to the physio/doctor for sportsmen and women at every level of competition are the result of musculoskeletal injuries. These injuries to muscles, tendons, ligaments, bones and cartilage are often the result of weakness within the extracellular matrix (ECM). In bone for example, the ECM is like the steel bars in reinforced concrete that increase the strength and ductility of the material. Therefore, strengthening the ECM has the potential to decrease sporting injuries. Beyond the role in injury prevention, ECM plays a further role in performance; increasing the rate of force development (one of the best measures of speed and power).

The ECM has long been considered an inert gel that just holds tissues together. In the last ten years, this view has been challenged by a number of experiments that demonstrate that the ECM is in fact a dynamic tissue that is essential to proper musculoskeletal function. For an athlete, the ECM has two main functions: 1) transmit forces quickly to maximize speed and performance; and 2) absorb energy from impact to prevent injury. Central to the first role are the ECM of muscle and tendon, whereas the second role also includes the ECM in ligaments, cartilage, and bone as well. Below, I will discuss how exercise and nutrition can maximize both functions.

ECM function is determined by the amount and cross-linking of collagen and the water stored within the tissue. The amount of water within the ECM does not appear to change appreciably with training, therefore for the ECM to become stiffer and stronger requires an increase in the amount of collagen or the number of cross-links binding the collagen proteins together. Cross-linking can be increased enzymatically (lysyl oxidase and prolyl-4-hydroxylase) or non-enzymatically (glucose-derived cross-links). In general, the enzymatic cross-links are beneficial and are regulated by exercise and nutrition, whereas the glucose-derived cross-links are detrimental and lead to many of the negative secondary outcomes of diabetes (high blood pressure, increased risk of tendon rupture, cataracts, etc.).

To maximize speed and power performance, coaches use high velocity movements with a significant plyometric component. This type of training does two things to the ECM: 1) increases the collagen content and cross-linking within the muscle ECM; and 2) increases the cross-linking of the ECM in the muscle end of the tendon. The result is that force can be transmitted from muscle to bone faster resulting in an increase in speed and power.

To prevent muscle injuries, coaches and physical therapists use slow movements; either heavy weight training, slow eccentric movements, or heavy isometric holds. This type of training does two somewhat different things to the ECM: 1) it will still increase the collagen content and cross-linking within the muscle ECM; but unlike the fast movements this type of training will 2) decrease the cross-linking of the ECM in the muscle end of the tendon. Since the muscle end of the tendon functions as a shock absorber, decreasing stiffness in this region of the tendon will protect the associated muscle from injury.

Even though coaches have some tools improve muscle and tendon performance and injury rate, there are fewer tools to prevent injuries in ligaments, cartilage, and bone. This is largely because we haven’t really understood how these tissues respond to loading and nutrition. Recent advancements in this area provide hope for a new toolset to prevent stress fractures, and progressive ligament and cartilage degeneration

The first advance came from research in rodents and humans that showed that short loading protocols (5 and 40 loads) separated by >6 hours of rest were enough to maximize bone synthesis rates. Similarly, we showed that collagen synthesis in ligaments was maximized by short periods (5-10 minutes) of exercise separated by 6 hours of rest. These data suggest that, unlike muscle that continues to adapt as long as we exercise, our ECM only gets the signal to adapt for 5-10 minutes before the cells start shutting down. Everything after that is causing mechanical fatigue and damage without giving a further stimulus to adapt and get stronger.

This means that for our ECM we should be doing short periods of loading (5- minutes) that target the tendons/ligaments/bones/cartilage that we use in our sport (jump rope for runners, bench step ups for basketball players, rotator cuff exercises for baseball/water polo/cricket players). These training sessions should be performed at least 6 hours away from our other training (where possible). These protective sessions serve to stimulate ECM production and decrease the likelihood of repetitive stress injuries to bone, ligament, tendon, and cartilage.

Beyond the loading, we now know that we can promote ECM production nutritionally as well. In our most recent study, we combined the intermittent exercise with gelatin: a food source of the amino acids enriched in collagen (Shaw et al. 2017). In this randomized double-blind cross-over design study we had subjects consuming either a placebo, 5, or 15 grams of gelatin in ~500 ml of vitamin C rich (~50 mg) black current juice and determined the appearance rate of amino acids and the production of collagen over the first 4 hours of the intervention. To increase collagen synthesis, we had the subjects jump rope for 6 minutes one hour after taking the supplements. Consistent with the importance of short loading periods on collagen synthesis, the 6 minutes of jump rope doubled collagen synthesis in the placebo and 5g gelatin groups. Further, when the subjects consumed the higher gelatin load (15g) we observed a further 2-fold increase in collagen synthesis above that from simply jumping rope for 6 minutes on its own.

For coaches and athletes, this means that an athlete could add a 5-minute protective session an hour after consuming gelatin and at least 6 hours before or after their other training to improve their bone, cartilage, tendon and ligament health and prevent injuries or accelerate return to play.

This is an exciting and rapidly expanding area of research that promises to improve performance and minimize injuries as our understanding of the ECM grows.

Recently an interesting report was published by the US Department of Agriculture. The document sheds light on food consumption patterns in the United States and how these have changed over time. With obesity rising, with claims being made that there are links between certain foods and certain nutrients and obesity it is interesting to look at these trends and see how they correlate.

The report examines the amount of food available for consumption in the US between 1970 and 2014. The report focusses on loss-adjusted food availability data. These data are essentially obtained from the foods that are produced and available for consumption and corrected for food losses (food spoilage, plate waste and other losses) along the way. This gives an estimation of consumption per capita. This is different than other studies where a cohort of people is asked to record their food intake. Both approaches have their challenges and limitations but both provide estimations of food intake in a population and insights into trends.

What did the new study find? First Americans have been consuming more food from ALL food groups between 1970 and 2014. Even the consumption of fruit and vegetables is increased! But most notably, on average, Americans consume more foods that are high in added fats and oils, added sugar and sweeteners and grains than is recommended. They consume too few foods that are nutrients dense such as vegetables, seafood, low-at dairy products and fruit.

Over the same period we have seen a dramatic increase in obesity as well as type II diabetes. These data are more compatible with the idea that obesity is caused by eating too much and not necessarily by eating too much of one nutrient whether this is fat or carbohydrate, added sugar or anything else.

Data like this have limitations as indicated above. They are impossible to apply to an individual but are pretty good estimates of what is happening at a population level. There are also advantages of this methods over other methods of assessing dietary intake. For example, food intake records rely heavily on honest and accurate reporting of dietary intake (and it is generally known that these methods may underestimate true intake by 20-60% and may skew the data towards certain ingredients).

Hippocrates may have been right all along.

“It is very injurious to health to take more food than the constitution will bear, when, at the same time one uses no exercise to carry off the excess. For as aliment fills and exercise empties the body, the result of an exact equipoise between them must be to leave the body in the same state they found it, that is in perfect health”.

Download and read the full report here:

In a recent publication by Liam Anderson from Liverpool John Moores University and colleagues unique insights in English Premier League football (soccer for those across the pond) were obtained. The results of the study were also discussed in December 2016 at the ISENC Sports Nutrition conference in Newcastle (UK) by Dr James Morton. Six professional soccer players of Liverpool Football club were followed during training and matches in order to get a better insight in their energy expenditure and energy intake.

The researchers used the most accurate technique possible for free-living conditions to measure energy expenditure, an advanced technique called the doubly labelled water method. This technique uses different excretion rates of oxygen and hydrogen to calculate energy expenditure and is generally regarded as the gold standard. The investigators also obtained detailed nutrition intake information from the players on different days: match days, recovery days and training days.

Energy expenditure was on average 3566 kcal/day (but was of course higher on the match days and lower on recovery days). Energy intake on match days averaged 3789 kcal and on training days 2956 kcal. All these figures are similar to what has been reported in the literature previously.

Of course it is particularly interesting to see if the players meet the recommendations especially for match play. For example, it is recommended to have different carbohydrate intakes on match days or hard training days versus easier days or rest days, but carbohydrate intake should be centred around the days with a higher load. On rest days a carbohydrate intake of 5 g/kg may be sufficient whereas on match days, in preparation for match day and in recovery from matches intake would have to be closer to 7 g/kg to meet the carbohydrate requirements of match play and optimise glycogen resynthesis

The players reported an intake of 4.2 g/kg/day on training days and an average intake of 6.4 g/kg on match days. It is recommended to make sure that glycogen stores are fully replenished before a match by eating a diet relatively high in carbohydrate and that the day or days after carbohydrate intake is slightly elevated to make sure glycogen can be restored to high levels before the match. This did not seem to happen, so the authors concluded that carbohydrate intake around match days can be further optimised.

Players had no problem achieving recommendations for daily protein intake but what may be more important is the distribution of protein intake during the day and this is something that should be looked at as well.

There is a need for these very practical studies and even though they only provide descriptive data, they are very insightful and give clues to optimising nutrition in environments like the English Premier League.

Reference

The topic of low carbohydrate high fat diets (LCHF) or ketogenic diets for athletes is still hotly debated. I posted some thoughts in a blog recently but a few days a paper was published in the esteemed Journal of Physiology that studies the effects of different diets on metabolism and performance in elite athletes and one of these diets was a LCHF diet.

The study was performed at the Australian Institute of Sport in the lead up to the 2016 athletics season which included qualifiers for the Rio 2016 Olympics. They called it project supernova.

In this study they used very well trained athletes (21 race walkers) who were following a structured training program in 3 week blocks. The athletes were allocated to one of 3 diet groups. Some athletes completed more than 1 training block and thus also more than 1 diet).

A high carbohydrate diet: Overall macronutrient composition 60-65% of energy from CHO, 15-20% protein, 20% fat; Similar daily CHO intake, with CHO consumed before, during and after training sessions. The diet represents sports nutrition guidelines from 1990s.Periodised CHO availability: Same overall macronutrient composition as HCHO, but spread differently between and within days according to fuel needs of training as well as an integration of some training sessions with high CHO availability (high muscle glycogen, CHO feeding during session) and others with low CHO availability (low pre-exercise glycogen, overnight fasted or delayed post-session refuelling). This strategy represents current guidelines and evolving evidence around benefits of strategic training with low CHO availability.A LCHF diet: 75-80% fat, 15-20% protein, <50g/day CHO.

Measurements were performed before and after the 3 week period and included performance measurements as well as metabolic measurements.

The study demonstrated that there were NO benefits of a ketogenic diet versus a high carbohydrate, or periodised nutrition approach in elite endurance athletes. In fact, performance of high intensity exercise was not improved by 3 weeks of intensified training in the ketogenic diet group, while athletes consuming the other diets made substantial performance improvements.

The study also confirmed early findings that the LCHF diet resulted in reduced economy. In other words: more oxygen is needed to perform the same amount of work.

The consistent finding in all LCHF studies is that fat oxidation is increased when carbohydrate intake is decreased. This is not surprising or new as it was first observed in the 1920s and many times thereafter. The question is, is this an advantage? Or could this be a disadvantage?

There are three ways to look at the increase in fat oxidation. One can look at an increase in fat oxidation in the light of improvements of fat oxidation. (generally this is believed to be a positive effect). This is a common interpretation but not necessarily the correct one.

Another possibility is that the increase in fat oxidation is the result of impairments in the ability to oxidise carbohydrate. Generally, such impairments would not be a positive adaptation because it is known that for every athlete no matter how long they have been on a LCHF diet, at high intensity carbohydrate is required as a fuel. Fats cannot be used anaerobically.

Of course it is also possible that at the moderate intensities it does not make a lot of difference where the fuel is coming from. This is perhaps why we see in ultramarathons (where he average intensity is relatively low) athletes being successful with very high carbohydrate diets as well as very low carbohydrate diets.

So what can we conclude from all the studies to date?

Fat oxidation is increased if we reduce carbohydrate in the dietThere are adaptations in the muscle if we deprive the body of carbohydrate that favour fat metabolism and such changes have been seen even within 5 days. Some of the adaptations take place rapidly (others may take longer)There are no well controlled studies in humans that show performance benefits of carbohydrate restriction

If you are an elite athlete and need to compete at high intensities, the LCHF diet does not seem to be the way to go. Instead it may be best to periodise nutrition with strategetically planned low carbohydrate intake and high carbohydrate intake (Although in this study that approach was not superior to a high carbohydrate intake).

Reference

Probiotics are food supplements that contain live microorganisms which when administered in adequate amounts can confer benefits to the health and functioning of the digestive system, as well as modulation of immune function. In the general population, studies have shown that probiotic intake can improve rates of recovery from diarrhoea, increase resistance to gut and respiratory infections, promote anti-tumour activity and alleviate some allergic and respiratory disorders (1). Several studies in athletes also indicate that some strains of probiotic – lactobacillus and bifidobacterium species in particular – can be effective in reducing the incidence of the common cold (5). The evidence for this was explained in aprevious blog. However, the benefits of probiotics may extend beyond immunomodulation improvements of immune function and reduction of illness risk according to new research that indicates the gut microbiota can communicate in a bidirectional manner with the brain and thus influence mood, stress responses and sleep quality.

The microbiota-gut-brain axis

The basis of this is the recognition of the existence of a microbiota-gut-brainconnections between the microbiota, the gut and the brain (referred to as the microbiota-gut-brain axis) axis that can influence behaviour and cognition via the production of neurochemicals chemicals (neurochemicals) by commensal certain bacteria and probiotics (3). This system has probably evolved over the millennia during which animals have hosted bacteria in their gut for mutual benefit. The microbe-derived neurochemicals are the same as those produced by the host and there is some evidence from animal studies that these neurochemicals activate nerve endings in the gut and information is then transmitted to the central nervous system (6). Microbes and their metabolism can also be influenced in turn by neurochemicals including catecholamines (e.g. adrenaline and noradrenaline) produced by the human body in response to stress. These interactions likely explain what we like to call our “gut feelings”!

Reduction of stress responses by probiotics

The body’s stress response system maintains homeostasis. When we are exposed to stresses (heat, exercise, mental challenges etc) against various external stimuliour body adapts. However, an excessive response to stress can trigger both mental and physical health problems. Studies in animals have shown that probiotics and gut microbiota can reduce stress reactivity by modulating the neuroendocrine system and can have positive effects on behaviour and cognitive function (e.g. reduced anxiety, depression and defeatism) under stressful conditions. In humans, recent investigations of the effects of probiotics on both stress-related physical symptoms and stress biomarkers have shown beneficial effects.

New studies

A series of double-blind, placebo controlled trials in medical students studying towards a nationwide academic examination were conducted by researchers in Japan (2,6). For 8 weeks before the exam, two groups of 70 students, consumed either Lactobacillus casei Shirota (Yakult) in a fermented milk drink or a placebo milk drink daily. The self-reported scores for abdominal dysfunction and cold-like symptoms and the number of genes with more than a 2-fold change in gene expression in white blood cells were significantly suppressed in the probiotic group compared with the placebo group during the study period. Levels of the salivary stress hormone, cortisol, were also lower in the probiotic group close to the time of the exam. Thus, administration of the probiotic was shown to reduce stress-related physical symptoms and a hormonal biomarker of stress. At a recent conference that I attended in Tokyo, one of the researchers who led these human studies, Dr Kensei Nishida reported the results of his latest study which indicated that regular daily ingestion of Lactobacillus casei Shirota also improved sleep quality (earlier onset of sleep and longer sleep duration with probiotic compared with placebo) in medical students preparing for their academic exams (4).

Possible benefits for athletes

These findings raise the possibility that probiotics could be of benefit for athletes recovering from intensive training and competition. Recovery involves both physical and psychological issues and a supplement that could reduce physical symptoms of stress and improve both mood and sleep quality would almost certainly be good for the athlete or games player. The importance of mental as well as physical recovery after intense competition is often underestimated, but a quote from someone who has a lot of experience of these issues, Dr Sam Erith, head of sport science at Manchester City FC, is illuminating: “the longer I do this job the more you see that mood and mind state are such powerful drivers for recovery”. Although further research is required to confirm these effects in the sporting population, it seems likely that probiotic supplements may provide multiple benefits for athletes and games players.

References

1.Hao Q, Dong BR and Wu T (2015) Probiotics for preventing acute upper respiratory tract infections. Cochrane Database Systemic Review 2:CD006895.

2.Kato-Kataoka A, Nishida K, Takada M et al. (2016) Fermented milk containing Lactobacillus casei strain Shirota prevents the onset of physical symptoms in medical students under academic examination stress. Beneficial Microbes 7(2):153-156.

3.Lyte M (2014) Microbial endocrinology: Host-microbiota neuroendocrine interactions

influencing brain and behaviour. Gut Microbes 5(3):381–389.

4.Nishida N (2016). Stress relief effect of probiotics through gut-brain axis. Proceedings of the 8th Yakult Shirota Conference, Tokyo, 2nd November, 2016.

5.Pyne DB, West NP, Cox AJ and Cripps AW (2015) Probiotic supplementation in athletes: clinical and physiological effects. European Journal of Sports Science 15:62-72.

6.Takada M, Nishida K, Kato-Kataoka A et al. (2016) Probiotic Lactobacillus casei strain Shirota relieves stress associated symptoms by modulating the gut-brain interaction in human and animal models. Neurogastroenterology and Motility 28(7):1027-1036.

Nutrition influences the adaptive response of training on muscle mass and function. Thus, it is important to determine the nutrition and training stimuli for optimal training adaptations. Certainly, an evidence-based approach is crucial for generating the best nutrition and training recommendations. However, interpretation of the scientific literature can be problematic. Recently, the response of anabolic signaling pathways to various nutrition and exercise interventions has been investigated. More and more, practitioners are encouraged to consider this type of information to inform recommendations for athletes and other exercisers.

The primary molecular anabolic pathway that has been investigated is the mTORC1 signalling pathway (Figure 1). For over 20 years, the response of this pathway to nutrition and exercise has been studied in cell culture and animal models. It is quite clear that the activity of this anabolic-signaling pathway is critical for optimal stimulation of muscle protein synthesis (MPS) and thus muscle adaptation.

More recently, studies in humans have contributed more information. In fact, there are data showing a relationship between the response of the mTORC1 pathway and muscle hypertrophy. However, I would argue that use of data on the response of anabolic signaling pathways to nutrition and exercise interventions should not be the primary basis upon which practical recommendations should be made. There are a number of limitations to the measurement of the response of anabolic signaling that must be considered before using these data for anything more than interesting mechanistic information.

Here are some findings

Recent studies have clearly shown that blocking the mTORC1 pathway inhibits the response of MPS to resistance exercise and protein.We also know that protein (essential amino acids) and resistance exercise both independently stimulate the mTORC1 signalling pathways.Moreover, measuring the response of these pathways is cheaper and easier than measuring MPS or doing a long-term training study.

Thus, it is quite tempting to use this information alone to inform practical recommendations.

A big however!

However, recent studies from our laboratory (and others) have shown that there is often a mismatch between the responses of the anabolic signaling pathways and muscle protein synthesis. There are a number of methodological reasons why we see this mismatch. Measurements of signalling proteins are made in small biopsies from the muscle. Because of its invasive nature, investigators have to make decisions when to take the biopsies because for obvious reasons they cannot take biopsies every 5 min. If you can only take a few biopsies, the timing of the muscle biopsies in any given study may be an issue. Each measurement must be considered as a snapshot at the time the biopsy was taken.

Issue 1

If we see that a particular intervention, say whey protein ingestion, results in a greater molecular response at 2h after ingestion, how do we know that the response may not be greater with ingestion of another protein at 1h and that is sufficient for maximal stimulation of muscle protein synthesis?

Issue 2

Another issue is a potential threshold effect. Typically, the activity of the mTORC1 pathway is assessed by measuring phosphorylation of the proteins in the pathway. So, if a particular intervention (A) results in greater phosphorylation than intervention B, we would suggest that A results in greater muscle protein synthesis and is thus superior to B. however, there is evidence that phosphorylation only has to hit a certain threshold and the system in maximally stimulated. So, the response of MPS to A and B will be no different.

Issue 3

Finally, the measurement of phosphorylation as an indication of pathway activity can be problematic. Measurement of phosphorylation is, at best, semi-quantitative so the precision often leads much to be desired. Dr. Lee Hamilton, in our research group here in Stirling, has recently validated a quantitative method for measuring molecular activity in human muscle. However, despite the improved precision that this method provides, the previous two issues, snapshot information and the threshold effect still apply. So, the information gleaned from measuring anabolic signaling in humans in vivo is important to provide mechanistic understanding. However, the unavoidable limitations of the measurements prevent use of this information for informing practical recommendations.

Thus, nutrition or exercise interventions can not be based solely on information about anabolic signaling pathways and should not be utilized by practitioners.

This blog was written by Professor Kevin Tipton at Stirling University. Related blogs can be found here:

I grew up in Holland, a country where children drink a lot of milk. The milk came from a cow and other types of milk were rare. Nowadays there are many different types of “milk” on the market; all with health claims and some even with performance claims. When traveling with professional athletes I often see the old fashioned cow milk is replaced by “fancy” new versions of milk like almond milk, soy milk and coconut milk. When I ask athletes “why?”, they tell me it is “better” or “healthier”. But exactly what does that mean and what is the evidence for that?

First, it is important to realize that most of these drinks aren’t actually “milk”, even though they may look a bit like milk. They can also vary significantly from a nutritional point of view. We should refer to these drinks as milk beverages or milk-like drinks because they are not technically milk. We also read about the benefits of cow milk, and the superior effects of whey protein (one of the constituents of cow milk) for recovery? So which is better? Is there evidence?

Cow milk

Cow milk has been the milk of choice for humans for many years. We have been drinking cow milk for more than 10,000 years. We can buy different versions of cow milk: Full fat, 2% fat, 1%fat, and fat free milk. We can also choose organic versions of milk which means that it comes from cows raised without the use of growth stimulants and other artificial ways to boost milk production. These cows also eat organic food. In terms of composition, organic milk is not too different from other milk, same amount of protein and other nutrients, maybe a little more of the essential fat alpha-linolenic acid.

The long term health effects of cow milk will be discussed in a future blog, including the effects on bone density, cardiovascular disease and so on. For some individuals, the lactose found in animal milks can cause gastro-intestinal discomfort. Those who are lactose-intolerant can choose lactose-free version of cow milk.

Differences between whole milk, skim milk, reduced-fat (2 percent), low-fat (1 percent), and fat-free milks is their fat content (and as a result their energy content (kcal)). (Table 1)

Goat

This is real milk from goats. Goat milk has the same protein and calcium content than cow milk. It also has slightly less lactose than cow milk, but still enough to cause problems for individuals who are lactose-intolerant. Goat milk contains more calcium, more magnesium and more vitamin C than cow milk.

Sheep

Sheep milk is higher in protein than cow and goat milk (almost 15 grams of protein per glass), and also offers a little more calcium, vitamin B12, and folate. Although not as readily available, this seems a good alternative to cow milk. Again those with lactose intolerance may want to avoid this type of milk.

Milk-like drinks

These options are non-dairy but often called “milk” because they look so similar to the real thing. But when it comes to nutrition these beverages are quite different. All non-dairy beverages that come from seeds are lactose-free, giving plenty of options to those who are lactose-intolerant or choose to forego animal products.

Soy milk

Soy milk, made from ground soybeans and water, comes in plain and flavored, which tend to be a lot higher in added sugars. Each glass provides about 6 grams of protein, which supplies all of the essential amino acids. Soy milk also comes fortified with calcium, and vitamins D and B12 (which does not occur naturally in soy). This makes soy milk a good lactose- and animal-free substitute.

Rice milk

Much lower in protein, rice milk provides only one gram per glass but in some countries it may come fortified with calcium, and vitamins D and B12. Check the label because nutrients may vary significantly depending on the brand with some brands containing hardly any nutrients. Rice milk is often sold as a sweetened version. If this is the case sugar has been added and the drink will contain more calories.

Oat milk

Like rice milk, oat milk is naturally sweet and are more palatable non-dairy milk options. Often sugar is added and this beverage contains very little protein (less than 1 gram per glass).

Almond milk

This beverage is made out of ground almonds with water. This non-dairy drink is also very low in protein with just one gram per glass. Check the label for added sugar, calcium, and vitamin D, since it can be hit or miss on which brands carry these nutrients.

Hemp milk

This drink is made of ground hemp seeds. These seeds are rich in omega-3 and omega-6 essential fats, about four grams per glass and contains some vitamin E as well. Hemp milk contains about 0-5 grams of protein per glass.

Coconut milk

The composition of this non-dairy milk drink can very a lot, and therefore it is very important to check the label. The canned milk can contain a lot of fat or no fat at all. Sometimes coconut milk is fortified with Vitamin D but it really is predominantly fat and water.It has zero protein and little calcium.

In conclusion, although several milk like beverages are often used by athletes to replace cow milk, they are really no replacement at all. Cow’s milk and plant-based drinks are not nutritionally comparable foods. Soy milk may be the drink that is somewhat similar but most other milk-like drinks have very different compositions. Most of these milk-like drinks contain very little protein and sometimes these drinks can be loaded with sugar.

Milk is often used for recovery because it is a good protein source. Milk-like beverages like almond, coconut and hemp milk are no milk replacements as they contain little or no protein. Soy is the milk like drink with the highest protein content and would be a better replacement of milk especially for those who are lactose intolerant. For those interested mainly in recovery, the amino acid composition is important too and studies seems to indicate that this composition is somewhat favourable in cow milk.

Finally, it is always important to check the labels for the exact composition and to keep asking questions.

Earlier in the year, I attended the Symposium that celebrated the 10th anniversary of the IOC Diploma in Sports Nutrition. One of the speakers was Louise Burke from the Australian Institute of Sport. Her talk was to discuss pros and cons of the much talked about Low Carbohydrate High Fat (LCHF) diet. Last week I spoke with Dr Paoli from the University of Padova at a conference in Bologna. He presented some of his outstanding work on ketogenic diets. Both talks were a balanced view of the literature... so are these just fad diets? Or is it the next best thing for athletes?

Let’s start with the current advice to athletes. This advice is to periodize nutrition, to stress carbohydrate in training and competition when this is required and to reduce carbohydrate intake for specific purposes. Especially in the popular press but even in some scientific publications this picture is frequently distorted by LCHF or ketogenic diet advocates. It is sometimes said that the advice is to eats lots of carbohydrates at all times. This is not the advice! Another distortion that is often used is the statement that “scientists think that fat is not used at higher intensities of exercise”. That is also nottrue. Of course fat is used at higher intensities. Even at 85%VO2max fat is used, but at the same time carbohydrate is the unrefuted dominant fuel at those intensities. Patients who cannot use fat as a fuel have a good exercise capacity but cannot sustain this for long. Patients with McArdles disease who cannot use carbohydrate as a fuel have very poor exercise capacity but can go longer at low intensities.

LCHF and ketogenic diet advocates often refer to one study from the 1980s as THE evidence that this works. Every reference to improved performance with ketogenic diets goes back to this study. Who actually takes the time to read the paper will discover that the paper isn’t actually supporting some of the claims that are often made. The paper shows that a ketogenic diet results in no changes in endurance capacity at a low intensity. There was huge individual variation in endurance capacity between individuals, which is to be expected with open ended exercise at that (low) intensity. In fact there is one individual who has an abnormally large variation in endurance capacity that may have skewed this data. Regardless, the data of this study do not support a performance benefit of a ketogenic diet and this was not the conclusion the authors drew. Also, the exercise is at such low intensity that the relevance for athletes should be questioned anyway.

There are a number of studies that used a LCHF or a ketogenic diet and show no differences in performance or a decrement in high intensity performance. An example was discussed in this previous blog: "Low carb diet v high carb diet and cycling performance". If studies have demonstrated a tendency towards performance improvement, this has always been at low exercise intensities, where the type of fuel used probably doesn’t make a lot of difference, intensities that can be sustained by both carbohydrate or fat. The majority of short term studies show that LCHF diets may be detrimental to performance and LCHF advocates are usually quick to point out that there may not have been enough time to adapt. Therefore we will look at the few studies that were 4 weeks or longer:

Below are some studies (of 4 weeks or longer) that measured actual performance or endurance capacity:

Phinney et al 1983 (4 weeks)

No difference in endurance capacity at low intensity (62-64%VO2max) in 5 subjects on a ketogenic diet versus a mixed diet.

Helge et al 1996 (7 weeks)

Smaller training adaptations after 7 weeks with high-fat versus high-carbohydrate diet. Diet was not ketogenic, but carbohydrate intake was very low in individuals who were training 3-4 times a week.

Zajac et al 2014 (4 weeks)

Ketogenic diet or mixed diet for 4 weeks in a cross-over design in off road cyclists. Reductions in peak power were observed after ketogenic diet.

This study is sometimes quoted for improvements in performance because they also observed increased VO2 and lactate threshold, but these are mere artefacts of increases in fat metabolism. Glycogen depletion results in increased LT, this is not the same as a training effect and it also increases oxygen uptake at the same workload (decreased economy).

Fleming et al 2003 (6 weeks)

Authors report small decrements in peak power output and endurance performance in the high fat diet group (not ketogenic) versus the high carbohydrate group.

If we have missed a study that is 4 weeks or longer, and has measured endurance capacity of performance please email us at info@mysportscience.com and the study will be added.

Conclusion

There is currently no evidence in favour of a ketogenic diet for exercise performance. There is little evidence in general, but evidence is especially lacking in well-trained athletes, who train on a daily basis and compete at high intensity.

It is sometimes argued that the absence of evidence is not evidence of absence and that is correct but at the same time without evidence we are only talking about a theory and not scientific facts. All we can conclude at this point is that several studies have been conducted and no study has yet provided any evidence and if anything studies seem to suggest a reduction in high intensity performance.

In my discussion with Dr Paoli in Bologna, he suggested that the ketogenic diet is perhaps not something for athletes during the competitive season but could be a good way to prepare for the season. Although, again, we don’t have evidence to support these ideas, this is possible and intriguing. It is also completely in line with current guidelines, where you plan your nutrition according to your goals, sometimes high and sometimes low carbohydrate. Not one diet that is best for everyone and all purposes.

There is a need for more research and less cherry picking, more evidence and less “belief”. More actual measurements and less surrogate measurements. More discussions about well performed studies and facts and less about anecdotes, feelings and emotions.

The previous blog Time to rethink the protein intake guidelines for athletes? reported on a recently published study from the research group of Professor Kevin Tipton. Kevin and I used to share offices next to each other at the University of Birmingham, so I used this paper as an excuse to ask him some questions about the paper. The stuff you don’t read in the paper…

AJ: First of all, congratulations with a great study that keep challenging our think just when we think we have figured it all out and have optimised our recommendations! Thank you for taking the time to answer some of my questions that remained after reading the paper.

Let’s start with an obvious question. If 40 grams is better than 20 grams, where is the limit? Could greater intake be even better?

KT: I’m not sure 50-60g would provide an even better response. the mean increase from 20g to 40g in our study was about 20%. So, for a 100% increase in intake, there is only a 20% increase in muscle protein synthesis. Also, I reckon it’s worth noting the individual responses. There is quite a bit of variability. So, for some individuals I bet a bit more protein may be beneficial. However, for the vast majority, I don’t believe it would.

AJ: There is a term called the muscle full effect, to describe that above a certain protein intake there are no further effect on muscle protein synthesis?

KT: Do you mean is there a muscle full effect at all or in our study? Actually, I reckon the answer to both is probably yes. There seems to be sufficient evidence for this concept. And the muscle full effect may help explain some of our results.

AJ: With the findings of your recent study in mind, what is your recommendation now for those athletes who want to gain as much muscle as possible as fast as possible?

KT: My recommendation to athletes that want to gain as much muscle as possible is that the optimal amount of protein to consume after exercise likely depends on the exercise performed. At least that is how we are interpreting our results. I should note that we did not test this directly and this comparison must be done. Until then, 20g is likely enough for most doing a split routine. However, I am not ready to discount the notion that many larger individuals may need more if they’re doing a split routine. That notion still has not been directly tested. Our results must be limited to a whole body routine. With a whole body routine, perhaps 40g is better.

AJ: If you need 3 grams of leucine to maximally stimulate protein synthesis as suggested by others and we can ingest a larger amount of protein, does this suggest that the quality of the protein becomes a less important factor? (It is easier to ingest essential amino acids including leucine when you simply eat more protein)?

KT: That is a great question. I really don’t know. We are assuming 3g of leucine is enough, but is that not based, at least in part, on previous results showing 20g of whey (containing roughly 3g leucine) was optimal. If 3g of leucine is ideal, then you’re probably right. Not enough work on other types of proteins has been done. As far as I know the only dose studies on proteins other than whey were done in Stu Phillips lab with soy. There was a greater response with 40g soy than 20g. However, that study was done with old folks and 40g whey was still better. So, clearly more studies in proteins other than whey need to be done.

AJ: Do the results of your study suggest that an athlete would be better off taking 40 grams of protein 5-6 times a day?

KT: I don’t think we can assume you need 40g 5-6 times per day. Our results apply only to the time immediately after exercise. we did not measure the responses to resting or to times later after exercise.

AJ: Is there a risk that increasing the protein intake will go at the cost of carbohydrate intake and could this ultimately affect recovery, performance and/or muscle growth?

KT: I’m sure there is a risk. I’ve always argued, and I know you do too, that athletes must balance the various demands. There is no one size fits all and it is nonsensical to just adopt one particular concept for all situations.

AJ: Taken together your studies seem to show greater protein synthetic rates with smaller muscle groups than larger muscle groups. Could this have implications for training? For example: train smaller muscle groups at a time?

KT: I had not really thought about it in those terms, but I reckon you’re right. Again, I’m not sure how practical it would be to train one muscle at a time given time demands and the necessity for other training. Perhaps split routines are a better suggestion. However, you’re right that that is a good question for future research. Our study seems to have developed a lot of those future questions. Certainly more than we’ve answered. But, is that not usually the case.

AJ: Thanks a lot Kevin, it was a pleasure tapping into your knowledge as always and please keep us posted about the great work that you and your colleagues do at the University of Stirling!

Most athletes easily exceed the recommendations for daily protein intake. However, in order to optimise the effects of training, it is still important to understand the amount of protein needed in each meal. Studies have demonstrated that 20-25 grams per meal results in optimal effects. But a group of researchers from the University of Stirling led by Professor Kevin Tipton challenged this thinking! In this blog we will review the literature and discuss these new results.

Three independent studies suggested that 20 to 25 g of protein would be required to reach these optimal effects on protein synthesis (1,2,3). Ingesting higher amounts of protein than this (e.g., 40 g) did not further stimulate muscle protein synthesis after resistance exercise. Similar results have been reported at rest using whole food (lean minced beef) in young men and women where a moderate (~ 30 g protein) amount was just as effective as a high (~ 90 g protein) amount for stimulating muscle protein synthesis (3). Based on these studies, recommendations are currently to take 20-25g of protein per meal with 8-10 grams of essential amino acids and about 3 grams of leucine. If more protein is ingested, the amino acids are simply oxidized and/or excreted as urea.

However, recently it was suggested that larger amounts may be needed for optimal adaptations. Macnaughton et al (3) argued that in previous studies, smaller muscle groups were trained and when larger muscle mass is involved (as would be the case for most athletes and most practical situations), larger amounts of protein may be required. When these researchers at the University of Stirling in Scotland performed a study in which volunteers trained a larger muscle mass, and then consumed different amounts of protein, there were two main observations. The first one was that protein synthetic rates were lower than previous studies, possibly because the same amount of protein now had to be shared with a larger amount of muscle. In the figure above a comparison is made with an earlier study by the same research group (2). Secondly, they observed that ingesting 40 grams of protein resulted in greater protein synthesis than 20 grams of protein, in contrast to previous studies, including their own. The authors discuss that perhaps when larger muscle groups are trained, a higher protein intake is required.

This findings raise a lot of new questions about what the guidelines should be. It seems clear though that more studies are needed to distil new guidelines from these data. Till that time the current guidelines are a great starting point: 20-25g of protein, containing about 8-10g of essential amino acids and 3 grams of leucine at regular (3-4h) intervals.

References

1. Moore et al. Am J Clin Nutr. 89(1):161-168, 2009.

2. Witard et al Am J Clin Nutr 2014;99:86–95

3. Symons et al J Am Diet Assoc. 2009 109(9): 1582–1586

4. MacNaughton et al Physiol Reports 4:15, 2016

Wearable technology is estimated to be a $6 billion dollar industry, which is likely going to continue to expand rapidly. For athletes and support staff engaged in elite sport, this can be both a help and a hindrance when trying to maximise athlete performance. Most would agree that technology such as heart rate monitoring and GPS has advanced the area of sport science and provided valuable information to monitor athletes to improve performance and reduce injury and illness risk. But with this ever increasing access to technology and with companies having the opportunity to make significant amounts of money, it is more important than ever that we can see the forest for the trees.

While there are numerous types of technology available, two of the more recent and popular devices are in the area of sleep monitoring and brain training/stimulation. With respect to sleep monitoring, most companies do not divulge their algorithms used to calculate sleep and wake and most have not validated their product against the gold standard of polysomnography. So while there may not be safety issues associated with these devices, it is clear that many of these devices may not be providing the athlete with accurate data. Importantly, how the athlete responds to having an abundance of readily available data on their sleep (accurate or not) is an important consideration. Athletes who may be susceptible to ‘over-analysis’ or may have issues with stress and anxiety, may find that daily information about their sleep is burdensome.

Of more serious concern are the number of devices now available which claim to stimulate or modify brain activity. While neurofeedback (brain training) has become increasingly legitimised in peer-reviewed interventions for medical conditions such as epilepsy and post-traumatic stress disorder, the availability of brain stimulation devices is rapidly increasing. While future research may prove that these devices do indeed enhance performance, it seems incongruous that these are marketed to elite athletes with very minimal research or proof of safety.

When companies market many of the wearables, they use particularly clever techniques. Impressive graphics, testimonials and figures, graphs and data that appears to such the devices have been tested and peer-reviewed. For athletes and staff looking for a competitive edge, this kind of information can be particularly enticing and hard to overlook. No one wants to be the last to take advantage of the next great advancement sport science. This plays into the hands of the manufacturer and many elite sports institutions and clubs do not have the time to validate and test the equipment in their own population. Increasingly however, this is exactly what is needed. While some companies do their own product testing, including reliability and validity, determining the usefulness in specific populations is the ultimate goal. A healthy scepticism of claims, evidence and testimonials, whilst still exploring potential uses and advantages may provide the most positive outcome.

The following recommendations when considering using wearable devices has recently been proposed [1] : 1) the primary driving principle should be to first do no harm, and direct implications on athlete health and safety should be of utmost and initial concern; 2) following such considerations, questions should be asked regarding the scientific basis for the device and a search for scientific evidence should occur; 3) if there is no or minimal scientific evidence, data should be collected in situ, in a controlled manner where possible; 4) implications for the athlete should always be considered (e.g., too much information, unnecessary information or information that may cause stress and anxiety).

Technology has great potential to have a positive and significant impact on athletes. However, we must always be cognisant of what information is valid and reliable, how much information is too much and that the wellbeing and safety of athletes is of principal concern.

Reference:

Halson, S.L., J.M. Peake, and J.P. Sullivan, Wearable Technology for Athletes: Information Overload and Pseudoscience? Int J Sports Physiol Perform, 2016. 11(6): p. 705-706.

Tart cherry juice has become increasingly popular as a recovery aid and the scientific evidence seems to be growing. I caught up with Professor Glyn Howatsen who wrote an excellent blog on cherry juicefor mysportscience, based on the studies that his team and others performed. The results seem very promising but I still had a few questions and could not find the answers in the literature. So I asked Glyn for his expert opinion.

AJ: Hi Glyn, thanks for the great blog and for the willingness to answer a few more questions. I usually call it "the stuff you don't read in the papers". When I read the literature my conclusion is that the results of cherry juice studies are not uniform. I also get the impression that some results could be the result of an inability to completely blind subjects. What is your view on this?

GH: Results are not uniform form many variables, but function is shown consistently to change, which from an athletic perspective is absolutely critical. If metric like maximal voluntary contraction (MVC) return faster, then by inference your ability to produce power is also returning faster. If function is in good shape, then any subsequent training and competition will be completed close to optimal (or at least baseline). There is a real issue with blinding for many studies, so conceptually if the participants know about cherries, then there could be a placebo or participant belief effect.

However, most studies show improvement in other indices that are difficult to explain by a lack of blinding - mostly in inflammation. Perhaps some psychosomatic effect is possible, but I suspect that a little belief in an intervention will unlikely translate to modulation of IL-6 or CRP, for example. Although the taste of cherries are distinctive, most (but not all) use a cherry flavoured or fruit flavoured cordial that is matched for macro-nutrient value and the participants are told the trial is about the efficacy of a fruit juice, not cherries. Lastly, although some indices do not show an effect, there are no negative responses. Thus cherries do not seem to have detrimental effects.

AJ: How strong do you think the evidence is? From a practical point of view how promising is it? Is it worth the investment and is it indeed low risk?

GH: There is a good range of studies in isolated muscles (using high intensity eccentric contractions). This is all very interesting and provides some proof of concept, but they lack task specificity to what athletes might encounter. In a series of studies we (and others) have tried to use this intervention in Marathon running, simulated road race cycling conditions and simulated repeated sprint sports (football, for example). The bottom line is that the evidence is very promising and at the moment seems unequivocal. I think from my perspective the athlete and practitioner needs to weight up the risk/benefit balance. From the current evidence there is nothing to lose and everything to gain; at the very least you ensure that the athlete is getting a polyphenol-rich fruit portion.

AJ: You mention that it is only this type of cherries… What is so special? What is the most likely active compound?

There are plenty of cherries in the supermarkets (Morello, Bing and so on). These are the same genus (Prunus; the same as apricots, peaches, plums) and in the case of Morello, the same species. However, despite being the same species the cultivars are different and the phytonutrients found are also different. It is very much like wine, where soil, environment, geography and seasonal variations can influence the goodies in the cherries. Montmorency cherries, which are largely from North America, are rich in polyphenols and anthocyanins and it is these compounds, and their downstream metabolites (phenolic acids), that are thought to be the bio-active plant compounds.

AJ: Now lets turn this into practical recommendations. Studies are all different… different number of days, slight different doses etc. What would you say is the perfect dose…. If there is such a thing? How many days would you use it? Before or after the event, or daily during a period with a congested competition schedule?

Is there a better time of day to take it? Any other recommendations?

GH: If you know what the schedule is, then it makes sense to start taking the juice in the days leading up to and after the event/session. Routinely, where recovery and NOT adaptation is the primary concern (for example rugby and football) because playing schedules are congested, players will have it on the table at meal times. I do not know if co-ingestion with other foods affects absorption, but in most cases, participants are instructed to consume the beverage in the morning and the evening around meal times. I think the crux of the whole thing is to provide the substrate when there is trouble (strenuous exercise), so it can act on the potential negative effects (probably oxidative stress and inflammation). Given the pharmacokinetics (the absorption, digestion, action and excretion) intake in the morning and afternoon/evening seem pragmatic. I would personally be tempted to take the PM dose about an hour before bed to potentially facilitate a better nights sleep.

If you consume a concentrate (often diluted with 100-200 milliliters (3-7 fl oz) of fresh water) then you need 30 milliliters (1 fl oz ) of the concentrate taken twice per day. However, we have done some bioavailability studies and showed that the compounds we think are having an effect tend to peak and subside within a few hours. So, if there is a benefit of a ‘loading’ phase for 3-5 days then these compounds are perhaps being stores in tissue somewhere - I have my doubts! However, ALL studies used a loading phase and ALL show some benefit - the easy way to conclusively address this is to only supplement after the event and see if the responses are similar.

AJ: Now that would be a great study and important from a practical point of view. Please let us know when you have done this study. Or perhaps one of our readers now has a great idea for a research project. Thanks very much Glyn for your insights and please keep us informed about any new developments in this area!

In recent years there has been a growing interest in so-called ‘functional foods’. In broad terms these foods are proposed to have an additional benefits to human health beyond the caloric content; for example, some berries and cherries that are rich in dietary polyphenols have been show to improve vascular function. In some cases these foods have been proposed to have medicinal benefits and their consumption amongst the global population is widespread, to the point where the world market is estimated to be in excess of $177 Billion. The appeal of foods with bioactive compounds is of great appeal since they offer the consumer a relatively risk free alternative to pharmacological or supplement interventions that might have unwanted side effects or be contaminated in some way. Understandably, these foods and their derivatives are of interest to recreational exercisers and athletes because of the potential ergogenic effect and ability to improve athletic recovery (1).

There are many fruits and vegetables that the media are very quick to jump on and promote as the next wonder food; however there are few stories that have an evidence base to support what it says on the tin. A fruit that is emerging with a good deal of promise is tart Montmorency cherries. This specific cultivar of cherries is extremely high in numerous plant compounds that can provide antioxidant and anti-inflammatory properties and compares favorably with other fruit and tea beverages (Figure 1). The application of these fruits consumed whole, dried, as a juice or a concentrate are varied and numerous applications ranging from management of rheumatic conditions in humans to reducing inflammatory markers in a Petri dish to accelerating recovery following strenuous exercise. The latter of these, exercise recovery, is an area of huge importance for athletes, particularly when training schedules are frequent and competition schedules are congested.

Figure 1. A comparison of antioxidant capacity of fruit and tea beverages.

The story of Montmorency cherries in exercise recovery started 10 years ago at the University of Vermont and the Nicholas Institute of Sports Medicine and Athletic Trauma with Declan Connolly and Malachy McHugh (2). They showed, in an isolated muscle-damage model, that Montmorency cherry juice accelerated the recovery of function and reduced muscle soreness when compared to a placebo beverage. Since then a number of studies from various labs across the UK and USA have shown a positive effect, in at least one variable, with Montmorency cherry juice (Figure 2, summary), which range from isolated eccentric-induced muscle damage to applied strenuous exercise models (Marathon running, cycling, repeated days exercise and team sports play).

Figure 2: Summary of studies

The previous research showed mixed result on inflammation, oxidative stress and muscle soreness, which is probably due to methodological differences such as exercise mode and intensity. However, the most important aspect, from an athletic performance perspective, is that muscle function is consistently accelerated in the days following the strenuous exercise. These data have not gone unnoticed and Montmorency cherries are routinely used in recovery as an intervention by Olympic athletes, the NHL, the EPL, NCAA Division 1 football, professional road cycling, Premiership and International rugby, particularly in times of competition congestion.

Montmorency cherries are taken in a juice format; either a fresh pressed juice or most commonly in a concentrate, where 30 mls of the concentrate can be taken neat or diluted with 100-200 mls of water. Whilst the whole fruits are great to eat, each serving of juice and concentrate can offer between 60-90 cherries per serving (depending on product) and consequently offer a convenient of way to consume a good volume of the nutrients. Interestingly, all previous work has used a loading phase of several days, which means that you need to be well prepared before the strenuous exercise. However, this makes little sense because the primary plant compounds of interest, like polyphenols (including anthocyanins), that appear to be responsible for the positive effects are metabolised quickly and peak in blood 1-3 hours after consumption and subside to basal levels within ~8 hours. So conceptually, Montmorency cherries could be consumed twice a day following the strenuous exercise until the negative symptoms (function and soreness) have abated, without the need for a loading phase.

Sleep is also a critical element of exercise recovery, which is not always easy to achieve when travelling regularly or when fatigued or suffering with sore muscles. There is evidence to show that melatonin is also contained in Montmorency cherries and can help to improve sleep efficiency (3), which is a good index of sleep quality. Consequently, taking the juice about 1 hour before bed could be an effective way to improve sleep and hence recovery from training and competition.

In summary, Montmorency cherries are a rich source of numerous plant compounds that can be beneficial in exercise recovery, particularly in times of high volume training and competition congestion. The juice can be utilized following both mechanically challenging (like heavy resistance training) or metabolically taxing, or concurrent exercise bouts that will likely result in reduced function and increased soreness. A concentrate offers a simple way to consume the polyphenol-rich fruit; and when taken close to bedtime could also facilitate better rest through sleep. However, make sure the correct variety of cherry is used – not all cherries are created equal and the evidence for a positive recovery response is ONLY evident with Montmorency tart cherries.

References

1. Bell, P.G. McHugh, M.P., Stevenson, E., and Howatson G. (2014). The role of cherries in exercise and health. Scandinavian Journal of Medicine and Science in Sports, 24, 477-490.

2. Connolly, D.A.J., McHugh, M.P., Padilla-Zakour, O.I. (2006). Efficacy of a tart cherry juice blend in preventing the symptoms of muscle damage. British Journal of Sports Medicine, 40,679-683.

3. Howatson, G., Bell, P.G., Tallent, J., Middleton, B., McHugh, M.P., Ellis, J. (2012). Effect of tart cherry juice (Prunus cerasus) on melatonin levels and enhanced sleep quality. European Journal of Nutrition, 51, 909-16.

There's nothing like a cool pint after exercise on a warm day. But is this a good idea? In a previous blog I discussed the effects of binge drinking on recovery and these effects were not positive. However, others have argued that beer drinking, in moderation, can have positive effects, beer adds to hydration, it contains vitamins, especially B-vitamins and chromium. The malt and hops used in both lager and bitter contain flavonoids, which counter cell damage and help reduce the risk of cancer and heart disease.

Recently I was contacted by the producers of a TV program on Channel 4 (UK) called Food Unwrapped. This program looks into the origin of our foods and tries to find out the truth behind some common beliefs about food. In this series they were interested in finding out whether small amounts of beer could have positive effects after exercise.

We set up a little study with a few rugby players at the University of Birmingham and focused on the hydrating properties of beer. The group was divided in two and they all performed the same training. Afterwards they received either beer or water and we measured some markers of hydration. It turned out that water was slightly better than beer. Of course this was not a very well controlled clinical trial and really just used for illustration purposes but how does it compare to the real research out there?

In a previous blog I presented the results of a study by Professor Ron Maughan and colleagues who compared the hydrating properties of various beverages. It demonstrated that the beverage hydration index (how well fluid is retained in the body after consuming a drink) for beer (lager) was perhaps slightly lower than water and other beverages but this difference was small and not statistically significant.

Similar findings were reported by Dr Ben Desbrow who performed a number of studies (1,2) looking at the effects of alcohol containing beers on post exercise hydration. In their studies, beer failed to completely restore fluid balance within 4 hours, independent of the strength of the beer and the electrolyte content. They did observe however that a light beer (with 2.3% alcohol) combined with 50 mmol/L of added sodium was a more effective rehydration solution than the same beer with half the sodium content or a mid strength beer with or without 25 mmol/L of added sodium. (50 mmol/L would be roughly 3 grams of table salt per liter and 25 mmol/L, 1.5 grams per liter).

There are other claims as well. Claims about vitamin content, especially B vitamins but these content if generally low. There are also claims about phytonutrients in beer and especially the polyphenols within nonalcoholic beer have suggested to have some positive effects following endurance exercise (3). Such effect include reductions in inflammation and incidence of respiratory tract illness. These results have not yet been confirmed as far as I am aware and therefore we may need to be a little cautious with the interpretation of these findings.

It is sometimes suggested that beer provides a good source of calories. In most beers, however, most of the calories are derived from alcohol and alcohol is metabolized in the liver and not in the muscle. There are carbohydrates in beer but the carbohydrate content is relatively low (0.5-4 g/100ml). In one pint you will find 2.5-20 grams of carbohydrate giving you 10-80 kcal. Alcohol in the same drinks will give you 22-28 kcal. Beer can certainly help a little towards restoring carbohydrate stores.

Summary

In summary, beer in moderation and diluted or consumed with water can help post exercise hydration. There is a little carbohydrate in beer that can help restoration of energy stores. There is no reason not to have one beer, it will help a lot of people and athletes to relax, but we always have to keep in mind the negative effects of larger amounts of beer/alcohol.

References

3. Scherr, J., Nieman, D.C., Schuster, T., Habermann, J., Rank, M., Braun, S., . . . Halle, M. (2012). Nonalcoholic beer reduces inflammation and incidence of respiratory tract illness. Medicine and Science in Sports and Exercise, 44(1), 18–26.

Water and sports drink are thought off as drinks with great hydration properties whereas caffeine containing beverages such as tea and coffee and alcohol containing beverages such as beer are thought of as dehydrating. But how do these drinks really stack up? The volume and composition of ingested drinks have a strong influence on how rapidly they will leave the stomach and are absorbed in the small intestine. Of course the faster they are emptied from the stomach and the faster they are absorbed, the faster fluids will enter the body. However, it is not just about the speed at which fluids enter the body because if you pee out the same amount, the net effect is no fluid retention. The contents of a drink will modify both absorption and excretion. Some drinks will slow down the delivery of fluid, but may also slow down the excretion. Perhaps surprisingly no an had ever compared some of the most commonly consumed drinks.

Professor Ron Maughan and colleagues set out to compare a number of different drinks and capture the hydrating properties in what they called the beverage hydration index (BHI). Essentially, the index compares how much of a drink is retained 2 hours after consumption compared to the same amount of water. The higher the index the more fluid is retained in the body. The full paper is available online, but in brief, they compared 13 beverages. Seventy two volunteers consumed 1 liter of each of these drinks. For the next 2 hours urine was collected. 2 hours is a practical time because it is probably similar to normal drink consumptions patters (as opposed to 4 hours which was used in many previous studies).

The results demonstrated that some drinks had better hydrating properties than water. Perhaps not surprising is the fact that oral rehydration solutions scored the highest value. These heavily researched drinks deliver fluid fast and the high electrolyte content is responsible for fluid retention. But skimmed milk, whole milk, and orange juice also scored well. These drinks are higher in calories and have more ingredients that may slow down gastric emptying and absorption but result in an overall greater fluid retention.

The other effect that may be somewhat surprising to some was that beer (lager), coffee and tea had scores that were very similar to water. They certainly did not display the dehydrating properties that are often talked about. The difference between beer, coffee, tea and water was not statistically significant. It is likely that the dehydrating properties of alcohol and caffeine were counterbalanced by the fluid retaining properties of the other ingredients. It is also possible that alcohol and caffeine in very small amounts do not have diuretic effects. The early studies that demonstrated these properties were done with much larger amounts of alcohol or caffeine.

We can further learn ffrom this study that a number of beverages were pretty similar to water (sports drinks, tea, cola, diet cola).

So although some drinks are better than others at retaining fluids, most drinks will contribute to daily fluid requirements.

See also:

References

A couple of weeks ago a paper was published in the Journal of Physiology with the title “Post-exercise cold water immersion attenuates acute anabolic signalling and long-term adaptations in muscle to strength training”. Essentially the study compared the effects of cold water immersion and active recovery on changes in muscle mass and strength after 12 weeks of strength training. After 12 weeks of training, effects were better with active recovery versus cold water therapy.

In the past studies suggested that cold water therapy can reduce soreness and improve recovery he next day(s). The current study addresses the longer term effects (12 weeks) of training, not the short term effects. Dr Shona Halson discussed this recently in a very nicely balanced blog on mysportscience. The essence of her story, based on the balance of evidence: whether you should use an ice bath or not depends on your goal. If you want short term recovery (before the next heat or match, it helps recovery), if your main goal (a competition for example) is weeks away daily ice baths may not help you. In other words: the context is extremely important. If someone wants to recover quickly, an ice bath may be a good idea. One could argue that the evidence is not incredibly strong, but this paper did not do anything to weaken these arguments because they simply did not study these effects.

The authors of the paper in the Journal Physiology added a seemingly harmless word of caution at the end of their paper: Individuals who use strength training to improve athletic performance, recover from injury or maintain their health should therefore reconsider whether to use cold water immersion as an adjuvant to their training.

What happened next seems to be typical in the world of journalism today… It started with a press release from from QUT (Queensland University of Technology):

They wrote:

If the thought of a post workout ice bath is enough to make you shiver, new research from QUT and The University of Queensland (UQ) will warm your heart.

Really??

And the title of the press release was:

Research pours cold water on ice bath recovery theory

A good mark for catchy-ness, a poor mark for accuracy… Does the study our cold water on the theory? No! The study did not look at acute recovery, where ice baths seem to help. It looked at the long term effects. So the theory still holds, but it may also be important to consider the long term effects. But we knew this already… The problem is that the context is lost. If Andy Murray takes an ice bath between matches, is he interested in his performance 12 weeks later? Or does he want to be in the best possible shape back on court he day after?

The authors may be to blame a little as well because the following comment by one of the researchers was added to the press release: “the results suggested people should steer clear of ice baths -- at least after strength training sessions.”

This news was rapidly picked up by newspapers. And this is where the fun begins. A fight for the most provocative and attention grabbing headline:

Bin the painful ice baths - opt for a gentle cool-down instead, warn experts

The Independent, Ireland 5 Oct

Ice baths, treatment of choice for Andy Murray and Mo Farah, do not help post-exercise recovery - new research

The Telegraph 5 Oct

Sorry Mo (Farah), an ice bath does not help you recover

Daily Mail 5 Oct

Sorry Andy (Murray) and ice bath does not help you recover

Scottish Daily Mail, 5 Oct

Hot news for athletes: a gentle warm down is just as effective as an Ice bath

The Daily Telegraph, 5 Oct

In all these reports the balance is lost and the context is missing. It is about catchy one liners, not about meaningful content. The message that most readers will take away, is that ice bath don’t work. The newspapers had their headlines and it is up to practitioners who work with athletes on a daily basis to clean up the mess.

In this case everyone is to blame: the researchers, the University, the newspaper. And it is of course not an isolated case. More and more this seems to become the norm. Everyone loves a good headline, but let’s try to be less superficial than that..

Note: I am not a big believer in ice bath. There is some evidence though for acute effects. This article does not criticise the article in J physiol. I think it is a great paper, a solid study that provides further support for existing thoughts and is aligned with other work. This blog is about the reporting of science in the media and how we communicate science from a lab and bring this to the masses.

Related blogs:

What are probiotics?

Probiotic-rich foods and supplements contain non-pathogenic bacteria that colonise the gut and can potentially yield a variety of health benefits that include reduced incidence of respiratory and gastrointestinal illness. There are several possible ways in which probiotics can act to produce these effects. By their growth and metabolism, probiotics help inhibit the growth of other bacteria, antigens, toxins and carcinogens in the gut, and reduce potentially harmful effects. Probiotics can also influence immune function via interaction with immune cells associated with the gut. Probiotics are found in several foods, particularly dairy products such as milk, yoghurt and cheese, although concentrations are relatively low. Consequently, there is widespread interest in use of probiotic supplements in both the general and sporting communities.

Potential health benefits of probiotics

Probiotics have been used for over a century to manage common gastrointestinal conditions including stomach cramps, irregular bowel movements, excessive flatulence, diarrhoea, and irritable bowel syndrome. In research settings, the focus has been on verifying the clinical benefits of regular probiotic supplementation, and underlying mechanisms of action. Many studies have been conducted on the effects of probiotic use on gastrointestinal problems and upper respiratory tract infection (URTI) in the general population. A recent systematic review (King et al 2014) of 20 placebo-controlled trials in both children and adults concluded that probiotic use resulted in lower numbers of illness days, shorter illness episodes and fewer days of absence from school or work. The most recent Cochrane systematic review of probiotic benefits for URTI using data from randomised controlled trials involving 3,720 non-athletes from 12 studies concluded that probiotics were better than placebo in reducing URTI incidence by 47%, and the average duration of an acute URTI episode by 2 days (Hao et al 2015).

The most important mechanisms of probiotic action are thought to be via influences on local immunity (by interaction with gut-associated lymphoid tissue and maintenance of gut barrier function) and systemic immunity (by enhancing some aspects of both innate and acquired immune responses). Certain probiotics, particularly those containing Lactobacillus or Bifidobacterium species, have been shown to enhance several aspects of immune cell functions including natural killer cell activity, microbicidal capacity of neutrophils and monocytes, modify the production of cytokines and elevate levels of antibodies (Hao et al. 2015), with effects that can extend beyond the gut to other mucosal sites, including the respiratory tract.

Evidence of probiotic benefits for athletes

A recent comprehensive review (Pyne et al 2015) identified 15 relevant experimental studies that investigated immunomodulatory and/or clinical outcomes of regular probiotic use in athletes. Of the 8 studies that recorded URTI incidence, 5 found reduced URTI frequency or fewer days of illness and 3 reported trivial or no effects. A randomised, placebo-controlled trial involving physically active individuals (West et al 2014) reported that 27% fewer URTI episodes were experienced in those who ingested daily a Bifidobacterium probiotic compared with placebo over a 150-day intervention period. The studies that have shown reduced URTI incidence in athletes have been mostly limited to Lactobacillus and Bifidobacterium species and used daily doses of ~1010 live bacteria. Although most studies have examined probiotic effects in relatively small numbers of recreationally active individuals over periods lasting less than 6 months, there is now sufficient understanding of the mechanism of action of certain probiotic strains, and enough evidence from trials with athletes and highly physically active people (in addition to 12 studies cited in The Cochrane review (Hao et al. 2015) on children and adults) to signify that there are mostly positive effects.

Other potential benefits of probiotics could be reduced risk of gastrointestinal discomfort symptoms and diarrhoea (e.g. so-called runner’s trots) during prolonged exercise, reduced endotoxaemia during exercise in the heat, and reduced incidence of gastrointestinal infections – a particular concern when travelling abroad. Future research is likely to establish the long-term tolerance of probiotic supplementation in highly-trained athletes over several months to years, the possible benefits, if any, of cycling on and off probiotics, and the effectiveness of multi-component formulations combining several different probiotics species, or probotics and prebiotics (non-digestible food ingredients that promote the growth of beneficial microorganisms in the intestines).

Practical application and advice

Take a daily dose of probiotic containing Lactobacillus and/or Bifidobacterium species containing at least ~1010 live bacteria (referred to as colony forming units, CFU). This is probably better than multi-strain probiotics as different strains can produce different effects which may oppose each other. Take the probiotic in the morning with breakfast. Probiotics need to be taken for several weeks before positive health effects can be expected.

References

Hao Q, Dong BR and Wu T (2015) Probiotics for preventing acute upper respiratory tract infections. Cochrane Database Systemic Review 2:CD006895.

King S, Glanville J, Sanders M, Fitzgerald A and Varley D (2014) Effectiveness of probiotics on the duration of illness in healthy children and adults who develop common acute respiratory infectious conditions: a systematic review and meta-analysis. British Journal of Nutrition 112:41-54.

Pyne DB, West NP, Cox AJ and Cripps AW (2015) Probiotic supplementation in athletes: clinical and physiological effects. European Journal of Sports Science 15:62-72.

West NP, Horn PL, Pyne DB, Cripps AW, Gebksi V, Lahtinen S and Fricker PA (2014) Probiotic supplementation for respiratory and gastrointestinal illness symptoms in healthy physically active individuals. Clinical Nutrition 33:581-587.

We (humans) are a host to many many microbes - bacteria, fungi, protozoa and viruses. In fact, there are trillions of them. That is more than we have cells in the human body. It was often assumed that the the number of microbes outnumbered the number of cells in the body by about 10-fold, but more recently this myth was busted. The majority of these microbes live in our gut, particularly in the large intestine. In total these microbes may weigh as much as 1.5-2.5 kilograms (3-5 pounds).

The term microbiome although technically meant to represent the genetic material of all the microbes, is often used to describe our collection of microbiota. The microbiome could be regarded as the human equivalent of an environmental ecosystem. Because the existence of the microbiome was not generally recognized until the late 1990s, our understanding is still in its infancy.

The bacteria in and on our bodies are likely involved in a number of important functions. For example:

1. The microbiome helps digest our food,

2. Regulates our immune system

3. Protects against other bacteria that cause disease, and

4. Produces vitamins including several B vitamins (vitamin B12, thiamine and riboflavin) and Vitamin K.

Role of the microbiome

The microbiome is essential for human development, immunity and nutrition. Thus the bacteria living in and on us are not invaders but beneficial colonizers. Autoimmune diseases such as diabetes, rheumatoid arthritis, muscular dystrophy, multiple sclerosis, and fibromyalgia have been associated with dysfunction in the microbiome. Disease-causing microbes accumulate over time, changing gene activity and metabolic processes and resulting in an abnormal immune response against substances and tissues normally present in the body. It has been suggested that autoimmune diseases are passed in families not by DNA inheritance but by inheriting the family’s microbiome.

Studies also suggest that the gut microbiome is different between obese and lean twins. Obese twins have a lower diversity of bacteria, and higher levels of enzymes, meaning the obese twins are more efficient at digesting food and harvesting calories. Obesity has also been associated with a poor combination of microbes in the gut. Some have suggested that the variety of gut microorganisms is decreasing as a result of changes in diet and this is the cause of disease.

A word of caution

There has been a huge interest recently in the microbiome and its role in health, disease and even performance. There has been a lot of attention in the media and a huge hype has been created around it. It is important to realize that the microbiome plays a role, but its role is also often exaggerated. We have a lot to learn still and it is too early to draw very firm conclusions. An article in the Times was titled “We are our bacteria” seemed to suggest a dominant role of bacteria in our bodies.

There are many claims and not a lot of conclusive answers yet. All we know is that many claims are based on correlations and these do not necessarily need to be causal relationships. Drawing simplistic conclusions from incredibly complex systems such as the microbiome, are likely to be flawed. So next time your read about the microbiome please keep this in mind.

An important way to explore the role of the microbiome for athletes is by altering the microbiome and studying the effects. Currently, one of the easiest and main dietary strategies to change gut microbiota is the use of probiotics. In a next blog Professor Mike Gleeson will discuss the effects of probiotic supplementation in athletes.

The prevention of illness is a key component in athlete health management. Illness prevention strategies are not only important to optimise uninterrupted training, but also to reduce the risk of illness that can prevent participation in important competitions. In this second article on prevention strategies we examine current guidelines on nutritional strategies to maintain robust immunity, managing the training and competition load, proactive psychological stress management and implementing the monitoring of athletes to detect early signs and symptoms of illness, overreaching and overtraining (Schwellnus et al. 2016).

Nutritional strategies

The athlete support team can consider adopting nutritional measures to maintain robust immunity in athletes (Gleeson 2016), including the following:

Introduce personalised nutrition programs to avoid deficiencies of essential micronutrientsEncourage athletes to ingest carbohydrate during and after exercise and to ingest both carbohydrate and protein after exerciseMeasure and monitor the vitamin D status of athletes and supplement if requiredConsider advising athletes to ingest probiotic such as Lactobacillus probiotics on a daily basisConsider advising athletes on the regular consumption of fruits and plants, polyphenol supplements (e.g. quercetin), or foodstuffs (e.g. non-alcoholic beer and green tea) that may reduce risk of illness

Training and competition load management

There is evidence that poor load management with ensuing maladaptation can be a significant risk factor for acute illness and overtraining. However, data are limited to a few select sports and athlete populations, and this, combined with the unique nature of different sports make it difficult to provide sport-specific guidelines for load management. However, the following general recommendations can be made:

Athletes should have a detailed individualised training and competition planning, including post-event recovery measures (encompassing nutrition and hydration, sleep, and psychological recovery)The training load is monitored using measurements of external and internal loadThe competition load is monitored and managedVariation in an athlete’s psychological stressors should guide the prescription of training and/or competition loadsIt is recommended that coaches and support staff schedule adequate recovery, particularly after intensive training periods, competitions and travel, including nutrition and hydration, sleep and rest, active rest, relaxation strategies and emotional support.

Psychological load management

Psychological load (stressors) such as negative life event stress and daily hassles can significantly increase the risk of illness in athletes. Practical recommendations centre on reducing state-level stressors and educating athletes, coaches and support staff in proactive stress-management, and comprise the following:

Developing resilience strategies that help athletes understand the relationship between personal traits, negative life events, thoughts, emotions, and physiological states, which, in turn, may help them minimise the impact of negative life events and the subsequent risk of illnessEducating athletes in stress-management techniques, confidence building, and goal setting, optimally under supervision of a sport psychologist, to help minimise the effects of stress and reduce the likelihood of illnessReducing training and/or competition loads and intensities to mitigate illness risk for athletes who appear unfocused as a consequence of negative life events or on-going daily hasslesImplementing periodical stress assessments (e.g., hassle and uplift scale) to inform adjustment of athletes’ training and/or competition loads. An athlete who reports high levels of daily hassle or stress could likely benefit from reducing the training load during a specified time period to prevent potential fatigue, illness, or burnout

Measuring and monitoring for early signs and symptoms of illness, overreaching and overtraining

The use of sensitive measures to monitor an athlete’s health can lead to early detection of symptoms and signs of illness, early diagnosis and appropriate intervention. Athletes’ innate tendency to continue to train and compete despite the existence of physical complaints or functional limitations, particularly at the elite level, highlight the pressing need to use appropriate illness monitoring tools. It is recommended that:

On-going illness (and injury) surveillance systems should be implemented in all sportsAthletes be monitored, using sensitive tools, for sub-clinical signs of illness such as non-specific symptoms and signs, or selected special investigationsAthletes be monitored for overt symptoms and signs of illnessAthletes be monitored for early symptoms and signs of overreaching or overtrainingIllness monitoring should be on-going, and long enough to detect early indicators of illness particularly during alterations in training load, travel and competitions

Strategies to reduce illness risk in athletes

Related:

References

Gleeson M (2016) Immunological aspects of sport nutrition. Immunology and Cell Biology 94:117–123.

Schwellnus M, Soligard T, Alonso JM, Bahr R, Clarsen B, Dijkstra P, Gabbett TJ, Gleeson M, Hägglund M, Hutchinson MR, Van Rensburg CJ, Khan K, Meeusen R, Orchard JW, Pluim BM, Raftery M, Erdener U, Budgett R and Engebretsen L (2016) How much is too much? (Part 2) International Olympic Committee consensus statement on load in sport and risk of illness. British Journal of Sports Medicine 50(17):1043-1052.

In the previous blog "

A variety of behavioural, lifestyle and medical intervention strategies have been advocated (1, 2) to reduce the risk of illness in the athlete. These include advice to athletes, measures taken by medical staff, and the athlete support team.

Athletes are advised to:

Minimise contact with infected people, young children, animals and contagious objectsAvoid crowded areas and shaking hands and minimise contact with people outside the team and support staffKeep at distance to people who are coughing, sneezing or have a ‘runny nose’, and when appropriate wear (or ask them to wear) a disposable maskCarry insect repellent, anti-microbial foam/cream or alcohol-based handwashing gel with themNot to share drinking bottles, cups, cutlery, towels etc. with other peopleChoose beverages from sealed bottles, avoid raw vegetables and undercooked meat, wash and peel fruit before eating, while competing or training abroadPractice the principles of safe sex and use condoms

Medical staff taking care of athletes are advised to consider the following:

Develop, implement, and monitor illness prevention guidelines for athletes and medical and administrative support staffScreening for airway inflammation disturbances (asthma, allergy and other inflammatory airway conditions)Identify the high risk athletes and take full preventative precautions during high risk training or competition periodsArrange for single room accommodation during tournaments for athletes with heavy competition load or known susceptibility to respiratory-tract infections, or high performance priority athletesConsider protecting the airways of athletes from being directly exposed to very cold (below 0°C) and dry air during strenuous exercise by using a facial maskAdopt measures to reduce the risk of illness associated with international travelUpdate athletes vaccines needed at home and for foreign travel and take into consideration that influenza vaccines take 5-7 weeks to take effect, intramuscular vaccines may have a few small side effects, vaccinations are performed preferably out of season, and avoid vaccinating just before competitions or if symptoms of illness are presentUpdate administrative and support staff vaccines needed at home and for foreign travelConsider zinc lozenges (>75 mg zinc/day; high ionic zinc content) at the onset of upper respiratory symptoms, as there is some evidence that the number of days with illness symptoms can be reduced

Continue to read about strategies to reduce illness risk in athletes in

Related:

References

1. Gleeson M and Walsh N (2012) The BASES Expert Statement on Exercise, Immunity and Infection. Journal of Sports Sciences 30(3):321-324.

2. Schwellnus M, Soligard T, Alonso JM, Bahr R, Clarsen B, Dijkstra P, Gabbett TJ, Gleeson M, Hägglund M, Hutchinson MR, Van Rensburg CJ, Khan K, Meeusen R, Orchard JW, Pluim BM, Raftery M, Erdener U, Budgett R and Engebretsen L (2016) How much is too much? (Part 2) International Olympic Committee consensus statement on load in sport and risk of illness. British Journal of Sports Medicine 50(17):1043-1052.

A pdf of a vertical version of the infographic can be purchased from for £5. This can be printed in any desired size without losing resolution. To be used to remind athletes of these 16 important principles in lorckerrooms, dining areas or other facilities.

We all suffer from colds at some time but recent research indicates that a person’s level of physical activity influences their risk of respiratory tract infections such as a cold, most likely by affecting immune function. Moderate levels of regular exercise seem to reduce our susceptibility to illness compared with an inactive lifestyle but long hard bouts of exercise and periods of intensified training put athletes at increased risk of colds and flu.

Upper respiratory tract infections (URTIs) are the most common ones that people get and include the common cold, sinusitis and tonsillitis. Most are due to an infection with a virus. The average adult has two to four URTIs each year and young children have twice as many. We are constantly exposed to the viruses that cause these infections, but some people seem more susceptible to catching URTIs than others. Every day our immune system protects us from an army of pathogenic microbes that bombard the body. Immune function is influenced by an individual’s genetic make-up as well other external factors such as stress, poor nutrition, lack of sleep, the normal ageing process, lack of exercise or overtraining. These factors can suppress the immune system, making a person more vulnerable to infection.

Exercise can have both a positive and negative effect on the functioning of the immune system and can influence a person’s vulnerability to infection. Researchers have found a link between moderate regular exercise and reduced frequency of URTIs compared with an inactive state and also with excessive amounts of exercise and an increased risk of URTIs. A one year study of over 500 adults found that participating in 1-2 hours of moderate exercise per day was associated with a one third reduction in the risk of getting a URTI compared with individuals that had an inactive lifestyle (Nieman et al. 2011). Other studies have shown that people who exercise 2 or more days a week have half as many days off school or work due to colds or flu as those who don’t exercise.

However, more is not always better in terms of exercise volume as other studies have reported a 2 to 6 fold increase in risk in developing an URTI in the weeks following marathon (42.2 km) and ultra-marathon (90 km) races. This is due, in part, to increased levels of stress hormones like adrenaline and cortisol that suppress white blood cell functions. After strenuous exercise, athletes enter a brief period of time in which they experience weakened immune resistance and are more susceptible to viral and bacterial infections, in particular URTIs. Post-exercise immune function depression is most pronounced when the exercise is continuous, prolonged (>90 minutes), of moderate to high intensity (55-75% of aerobic capacity), and performed without food intake (Gleeson et al. 2013). Another problem for athletes is that their exposure to pathogenic (disease causing) microorganisms in the environment may be higher than normal due to increased rate and depth of breathing during exercise (increasing exposure of the lungs to airborne pathogens), exposure to large crowds and frequent foreign travel. Some of the reported sore throats may not be due to infectious agents but to non-infectious airway inflammation caused by allergies or inhalation of pollutants and cold dry air.

A common perception is that exposure to cold wet weather can increase the likelihood of catching the common cold but the available evidence does not support this. Most people are more susceptible to colds in winter (which is possibly due to reduced vitamin D status at this time) but numerous studies on athletes indicate that they tend to be most susceptible to picking up infections at times close to competition. This usually follows a period of intensive training and added mental stress with the anxiety of wanting to perform well. The worry for athletes is that even a mild infection can impair their ability to perform at the highest level. Preventing infections is therefore very important to them and they can help themselves by ensuring good personal hygiene, good nutrition and minimizing other life stresses.

These illness prevention strategies are discussed in future articles in the following blogs:

Strategies to reduce illness risk in athletes

Related:

References

Gleeson M, Bishop NC and Walsh NP (2013) Exercise Immunology. London: Routledge (Taylor and Francis). ISBN 978-0-415-50725-7 (Hb); 978-0-415-50726-4 (Pb); 978-0-203-12641-7 (Ebook).

Nieman DC, Henson DA, Austin MD and Sha W (2011) Upper respiratory tract infection is reduced in physically fit and active adults. British Journal of Sports Medicine 45:987-992.

The frequency of acute illness in elite level athletes during international competition has been studied in a variety of settings including the Summer and Winter Olympic Games, Winter Youth Olympic Games, Summer and Winter Paralympic Games, and other international athletic and aquatic sport competitions (Table 1). These data indicate that in major international games lasting 9-18 days, 6-17% of registered athletes are likely to suffer an illness episode. Interestingly, illness appears to be consistently more common in female athletes compared with their male counterparts, which is the opposite of what is found for the general adult population. Furthermore, the incidence of illness appears to be higher in winter compared with summer Olympic Games and data from one study indicate that athletes with disability participating in the Paralympic Games appear to have a higher incidence of illness than athletes competing in the Olympic Games.

The most common illnesses are those affecting the respiratory tract with most studies indicating that about 40-60% of all acute illness episodes in athletes during competitions and tournaments affect the respiratory tract. Common symptoms of an upper respiratory illness include a sore throat, headache, fatigue, runny nose and/or watery eyes. Other parts of the body commonly affected by illness are the digestive system (10-20%), skin and underlying tissues (10-15%) and the genitourinary system (5-10%). Infections are generally reported as the most common cause of acute illness, with infection being the cause of respiratory tract illness in about 75% of cases. However, it is acknowledged that athletes can develop symptoms (e.g. sore throat, sinus congestion, cough) that mimic an infection but that the symptoms can be due to allergy or inflammation from other causes such as inhalation of cold, dry or polluted air.

Acute illness can cause a reduction in exercise performance, an interruption to training, and even result in missing an important competition. Acute infective illness can affect a number of organ systems causing a reduction in exercise performance through a number of mechanisms including: impaired motor coordination, decreased muscle strength, decreased aerobic capacity, and alterations in metabolic function. Furthermore, the presence of fever causes a decrease in the body’s ability to regulate body temperature and increases fluid losses, thereby impairing endurance performance. It has also been documented that a decrease in exercise performance after full recovery from a respiratory illness can last for 2 to 4 days and data from one study indicates that runners who start an endurance race with systemic symptoms of an acute illness are 2-3 times less likely to complete the race. It has also been reported, that in 33% of cases, an infection (most commonly of the respiratory tract) was the reason why elite Great Britain athletes from 30 different Olympic sports miss training sessions, Perhaps more importantly, an acute infective illness can also increase the risk of serious medical complications and even sudden death during strenuous exercise.

Outside of competition, the most common illnesses in athletes (and in the general population) are also viral infections of the upper respiratory tract (i.e. the common cold) which are more common in the winter months. Adults typically experience two to four episodes per year, although this can be higher during intensified training and competition due to the additional physiological and psychological stress.

There are many potential risk factors that are associated with acute illness in athletes (Figure 1). There is now some convincing evidence that an increased training load, competition load, and psychological stress together with international travel may all be risk factors for illness in the elite modern-day professional athlete. Prolonged bouts of strenuous exercise have been shown to result in transient depression of white blood cell immune functions and it is suggested that such changes create an “open window” of decreased host protection, during which viruses and bacteria can gain a foothold, increasing the risk of developing an infection (Gleeson et al. 2013). Other factors such as lack of sleep and inadequate nutrition (particularly deficiencies of protein and essential micronutrients) can also depress immunity (Gleeson 2016) and lead to increased risk of infection. There are also some situations in which an athlete’s exposure to infectious agents may be increased, which is the other important determinant of infection risk.

References

Gleeson M (2016) Immunological aspects of sport nutrition. Immunology and Cell Biology 94:117–123.

Gleeson M, Bishop NC and Walsh NP (2013) Exercise Immunology. London: Routledge (Taylor and Francis). ISBN 978-0-415-50725-7 (Hb); 978-0-415-50726-4 (Pb); 978-0-203-12641-7 (Ebook).

Also check: International Olympic Committee consensus statement on load in sport

Athletes train hard, compete a lot and are subject to a lot of psychological stress. This in turn can increase the chances of injury, overtraining and illness. For elite athletes (and everyone else who trains hard and works or manages a family at the same time), it is about managing the total load.

The IOC brought together a group of experts to discuss the topic of load in sport and risk of injury, overtraining and illness. This resulted in two scientific publications (part 1 and part 2) that were published online this week in the British Journal of Sports Medicine. Both papers can be downloaded from the journal’s web site (1, 2).

The International Olympic Committee convened an expert group to review the scientific evidence for the relationship of load which they defined broadly to include rapid changes in training and competition load, competition calendar congestion, psychological load and travel and health outcomes in sport.

Part 1 focusses on injury, part 2 on overtraining and immune function / illness.

The papers also provide athletes, coaches and support staff with practical guidelines to manage load in sport. The consensus statements include guidelines for (1) prescription of training and competition load, as well as for (2) monitoring of training, competition and psychological load, athlete well-being and injury.

Immune function

With the Zika virus being the topic of so much discussion at the Rio Olympics and with several stories of athletes going home, unable to compete, because of illness (3), I wanted to focus on the importance of immune function and found Professor Mike Gleeson, one of the authors of the papers in BJSM, prepared to write a series of short guest blogs on the topic of immune function.

He will cover:

1. How often do athletes get ill at major competitions? Read now

2. How doe exercise training affect immune function?

3. How can we prevent illness and specifically what is the role of nutrition?

Professor Gleeson who is now Emeritus Professor at Loughborough University and who I had the pleasure of working with at the University of Birmingham, is a real expert in this field. Mike is consulting with several teams and athletes and including Queens Park rangers (QPR), Leicester City FC and the English Institute of Sport (EIS). (He can be contacted on m.gleeson@lboro.ac.uk)

References

1. How much is too much? (Part 1) International Olympic Committee consensus statement on load in sport and risk of injury

Torbjørn Soligard, Martin Schwellnus, Juan-Manuel Alonso, Roald Bahr, Ben Clarsen, H Paul Dijkstra, Tim Gabbett, Michael Gleeson, Martin Hägglund, Mark R Hutchinson, Christa Janse van Rensburg, Karim M Khan, Romain Meeusen, John W Orchard, Babette M Pluim, Martin Raftery, Richard Budgett, Lars Engebretsen

Br J Sports Med 2016;50:1030-1041 doi:10.1136/bjsports-2016-096581

2. How much is too much? (Part 2) International Olympic Committee consensus statement on load in sport and risk of illness

Martin Schwellnus, Torbjørn Soligard, Juan-Manuel Alonso, Roald Bahr, Ben Clarsen, H Paul Dijkstra, Tim J Gabbett, Michael Gleeson, Martin Hägglund, Mark R Hutchinson, Christa Janse Van Rensburg, Romain Meeusen, John W Orchard, Babette M Pluim, Martin Raftery, Richard Budgett, Lars Engebretsen

Br J Sports Med 2016;50:1043-1052 doi:10.1136/bjsports-2016-096572

3. Rio 2016 Olympics: Rower Graeme Thomas out of Games with illness. http://bbc.in/2b09bM8 (19 Aug 2016)

We often read that coffee or caffeine dehydrates you. Maintenance of fluid balance is essential to sustain human life and we are recommended to drink regularly and recommendations for daily fluid intake vary from 1.5-3.7 liters per day. It has also been suggested that beverages that contain caffeine (such as coffee) should not be included in these daily fluid requirement guidelines, because of its diuretic effect. It is even recommended to drink a glass of water with each cup of coffee or tea. Does caffeine or coffee really dehydrate you? Or can you drink these beverages and do they contribute to daily fluid requirements.

Caffeine can be a diuretic

Before I discuss a recent study I want to make one thing clear: caffeine CAN be a diuretic! When consumed in large doses (over 500 mg), caffeine elicits a diuretic effect and this is known for more than 80 years! 500mg is a very high dose to ingested as one dose or in one drink. For comparison 400mg per day is considered a moderate daily intake and an average cup of coffee may contain 80 mg (For amounts of caffeine in different beverages read this previous blog).

It is also important to know that regular caffeine consumption may lead to a tolerance developing against its diuretic effect. It has since been suggested that caffeine withdrawal of as little as 4 days is sufficient for tolerance to be lost. So if you are a regular coffee drinker the diuretic effect may be less, even at higher doses of caffeine.

Coffee and hydration study

In a study published in PLOSOne (Dr Sophie Killer was the first author of the study) we addressed the question: Can coffee contribute to daily requirements when consumed in normal daily life, or will it result in dehydration? Where previous studies had studied the short term effects of coffee or caffeine consumption, in this study we were more interested in the longer term effects. We wanted it to be the best and the largest study of its kind so recruited 50 male coffee drinkers and used not one but a wide range of techniques to assess hydration. The effects of coffee consumption were compared against water ingestion during 3 consecutive days. Physical activity was controlled, food and fluid intake was controlled and participants consumed either 4×200 mL of coffee containing 4 mg/kg caffeine or the same amount of water.

Total body water was calculated before and after the trials using Deuterium Oxide, urinary and haematological hydration markers were recorded daily in addition to nude body mass measurement and blood plasma was analysed for caffeine to confirm compliance.

At the end of a very long and labour intensive study it could be concluded that there were no differences between the caffeine and the water trials in any of the markers of hydration. Thus, these data suggest that coffee, when consumed in moderation by caffeine habituated males provides similar hydrating qualities to water.

So now, when we board a British Airways plane we can actually read that coffee and tea also contribute towards daily fluid requirements.

Reference

The study discussed here is available to download for free from the PLOSOne web site:

There is no question that caffeine can improve endurance performance. A large number of studies has confirmed this and the topic has been reviewed in several review paper including a recent one by Professor Lawrence Spriet (1). There are also dose response studies that seem to suggest that small doses can already have effects and larger doses are not necessarily better. It is important to note, however, that many studies used an exercise protocol of approximately 1 h duration and this seems to be an optimal duration for caffeine to have performance enhancing effects. In these studies caffeine is typically ingested 1 hour prior to exercise so that the caffeine concentration in blood peaks at the onset of exercise and stays relatively high for the duration of exercise. Recommendations are then extrapolated from these kind of studies.

Is caffeine late in exercise effective?

For longer events of more than 2 hours the approach of taking caffeine prior to exercise may be more questionable. Athletes and coaches have often asked me whether it was a good idea to “peak” in the first hour and perhaps caffeine intake later in exercise would be preferable to avoid having to top up and ingesting larger amounts of caffeine. Very often I have been asked the question “can I take caffeine in the final hour?” Until recently, the answer to this question was rather speculative, but a recent study by Talanian and Spriet published in the Applied Physiology Nutrition and Metabolism addressed this question (2).

The study

The aim of the study was to assess if low and moderate doses of caffeine, delivered in a carbohydrate-electrolyte solution, ingested late in exercise improved time-trial performance. Fifteen (11 male and 4 female) cyclists completed 4 double-blinded randomized trials (after they had been made familiar with the methods). Subjects completed 4 times a 2h cycling test followed by a time trial that lasted roughly 30 min.

In order to make the tests more realistic, simulated hill climbs were included in the 2 hours of cycling. All trials were very well controlled (same temperature, same level of hydration of subjects, same nutritional patterns etc). Caffeine or placebo was ingested, 80 min into the 2h test (and thus 40 min before the start of the time trial). The cyclists received either no caffeine (placebo), 100 mg or 200 mg of caffeine.

The 4th trial one of these treatments was repeated. This is great practice from the researchers as it makes it impossible for the cyclists to guess what treatment they are on. It I a practice that I would love to see in more performance studies.

Findings

What did they find? The time trial was completed fastest with the moderate dose of 200mg, followed by the lower dose of 100mg. Both caffeine trials were faster than the placebo trial.

CAFFEINE 200mg (26:36 ± 0:22)

CAFFEINE 100mg (27:36 ± 0:32)

PLACEBO 0 mg (28:41 ± 0:38).

The authors concluded that both doses of caffeine, delivered late in exercise, improved performance over the placebo trial, but they also observed that the moderate dose improved performance to a greater extent than the low dose.

Lessons

There are a couple of important lessons to learn from this:

First it is ok to take caffeine late in exercise, but it is probably wise to take it 40-60min before the important “later section” of a race. For example, if in a bike race the final climb is 60 min before the finish, it would be recommended to take caffeine 40-60 in before that.

The optimal dose is probably individually determined and if you are affected by negative side effects of caffeine it is wise to reduce caffeine intake to a minimum. Without side effects, however, the study discussed here shows that 200mg was more effective than 100mg.

As a word of caution: this study does not mean more is better. Previous studies have demonstrated that higher doses are not more effective than moderate doses. Chances of side effects are greater with higher doses. These side effects include headaches, anxiety, increased heart rate, dizziness, nausea and gastro-intestinal problems.

What I love about this study is that it addresses a really practical question and the experiment was set up too mimic practical conditions. I also appreciate the care that has gone into measuring performance, which is quite remarkable. It would be great if this was the standard! Familiarisations trials, additional trials to avoid guessing, careful control of diet, exercise, temperature etc etc. The measurement of performance, may appear one of the easiest but is in fact the most difficult measurement in exercise physiology. Being able to measure small differences that are important to the athlete is only possible with careful execution.

References

1. Spriet. Exercise and sport performance with low doses of caffeine. Sports Med. 44 Suppl 2:S175-84.

2. Talanian and Spriet Low and moderate doses of caffeine late in exercise improve performance in trained cyclists APNM 41: 850-855, 2016

It has been a while since the last update in January but here is a list of approximately 100 sport scientists on twitter, scientists from different disciplines (psychology and biomechanics are still a little underrepresented).

A more complete list can be downloaded as a pdf here:

There are a few notable changes. Michael Joyner has been a lot more active on twitter and has shared some fantastic insights. As result his following has grown substantially. Other very active scientists in the last few months, who have also significantly increased their following include Yann Le Muer, David Bishop, Lorena Torres and Nanci Guest.

Below is a list of female scientists reporting on sports science issues. If the list is incomplete, please send me the names of those that need to be included. Criteria are:

1. must be actively publishing (peer reviewed) in areas relevant to exercise and sports

2. must convey (predominantly) evidence based messages and vast majority must be sport science related

3. must have a minimum of 500 followers

If you want to be included in this list please email detail to info@mysportscience.com for consideration

We all know that recovery is becoming increasing important and popular in athletes. As with most aspects of science, our expanding knowledge in the area only leads us to more questions. One of the more recent and controversial topics in the area of athlete recovery is can you recover ‘too much’?

Most athletes and coaches understand the principles of overload and supercompensation. We train, induce fatigue then recover. If these three components are dosed correctly a positive adaptation should occur. What this process highlights is that fatigue is an important part of the training process and necessary to induce adaptation. This then begs the question that if fatigue, muscle damage and inflammation are important to drive adaptation, could chronic or long term recovery actually be detrimental?

While there are a number of possibilities that may occur with chronic recovery (in particular cold water immersion or ‘ice baths’) two main theories exist. The first is that performing too much recovery may decrease the stimulus for adaptation. Might ice baths decrease inflammation and soreness and therefore lessen the trigger for adapting to the training the athlete has just completed. The other theory is that if the athlete is less sore and less fatigued then potentially they could train with enhanced quality and/or quantity. Add up the benefits of this increased training over months or years and this may provide significant benefit to the athlete.

So what evidence is available in the scientific literature to support or refute the above two theories. One of the first studies to look at this question involved investigating cycling or handgrip exercise three to four times a week for 4-6 weeks [1]. Overall cycling performance increased after training, however the leg that was immersed in the ice bath had a reduced performance when compared to the leg that did not have recovery. However, these subjects were not elite athletes and cooling protocol was extreme.

A more recent and elaborate study by Llion Roberts and colleagues [2] compared the effects of cold water immersion and active recovery on changes in strength after 12 weeks of training as well as effects on specific signalling pathways (triggers for muscle growth). Cold water immersion decreased gains in muscle mass and strength and blunted key proteins responsible for muscle growth. Again, the subjects in this study were not elite and were training only twice per week.

While the two above studies suggest that cold water immersion may be detrimental to performance, there are two further studies in cycling which suggest that performance may be increased by regular recovery.

We [3] investigated the effects of cold water four times per week or passive recovery over 7 d of baseline training, 21 d of intensified training, and an 11-d taper in highly trained cyclists. Cyclists in the cold water immersion group had increased in a range of sprint and high intensity cycling performance. Results suggest that hydrotherapy does not hinder adaptation to training and may indeed enhance a number of aspects of cycling performance.

Ishan and colleagues [4] investigated the effect of regular post-exercise cold water immersion (3 sessions per week of endurance training for 4 weeks) on muscle adaptation. Using muscle biopsies, the authors reported increases in markers that indicate improvements in endurance performance.

So with minimal research in the area and conflicting results found in the existing research, it is important to give consideration to a number of factors before making a decision on whether or not to include recovery in a training program.

These questions are important to ask for a number of reasons. The benefits of cold water immersion (when done correctly) on acute performance is well established. Therefore when an athlete is competing regularly (i.e. football or basketball seasons) or in a competition setting (i.e. swim meet, cycling stage race or rowing regatta), recovery can be extremely important to minimise fatigue and maximise performance. However if an athlete is in a regular training phase it is important to consider whether the athlete may be prone to injury or is excessively fatigued. If not this may be a time to reduce the amount of recovery an athlete receives. Recovery can also be used to prepare the athlete for upcoming training sessions. So if the coach is asking for high quality and high intensity training sessions, recovery may become important to allow this to occur.

It is becoming increasingly clear that the concept of periodisation is critical is sport science. While we periodise training, it is becoming increasingly popular to periodise nutrition. It is now time that coaches and support staff also consider periodising recovery. While many of us are looking for a simple and easy answer to whether or not we should use recovery, like many other aspects of sport science, the answer is not black and white. We must carefully consider both the type of athlete we are working with and the specifics of their sport and training program. By doing this we can identify the area between the black and the white and provide the athlete with the greatest opportunity for performance gains.

References

Yamane M, Teruya H, Nakano M, Ogai R, Ohnishi N, Kosaka M. Post-exercise leg and forearm flexor muscle cooling in humans attenuates endurance and resistance training effects on muscle performance and on circulatory adaptation. Eur J Appl Physiol 2006;96(5):572-80Roberts LA, Raastad T, Markworth JF, et al. Post-exercise cold water immersion attenuates acute anabolic signalling and long-term adaptations in muscle to strength training. J Physiol 2015;593(18):4285-301 doi: 10.1113/JP270570[published Online First: Epub Date]|.Halson SL, Bartram J, West N, et al. Does Hydrotherapy Help or Hinder Adaptation to Training in Competitive Cyclists? Med Sci Sports Exerc 2014 doi: 10.1249/MSS.0000000000000268[published Online First: Epub Date]|.Ihsan M, Watson G, Choo HC, et al. Postexercise muscle cooling enhances gene expression of PGC-1alpha. Med Sci Sports Exerc 2014;46(10):1900-7 doi: 10.1249/MSS.0000000000000308[published Online First: Epub Date]|.

The recent blog by Prof Neil Walsh on Train Cool - Bathe Hotcovered the scientific aspects of a publication on "heat acclimation through hot baths" (first author Mike Zurawlew). The findings of the study were presented in a very clear way, but often a research paper leaves the reader with a number of practical questions. Research is conducted in a very controlled way and it is sometimes difficult to extrapolate findings to different situations, populations or events. Therefore I caught up with Neil walsh and Mike Zurawlew and asked them about "the practical stuff that you don't read about in research papers"....

Neil and Mike, the conditions in the study you published were fairly extreme 33°C. How does this compare to conditions athletes may experience? (how extreme or how common is this?)

Yes, the conditions were challenging in the hot trial (33°C, 40% RH) in our study. Nevertheless, we present strong evidence that the intervention also reduces thermal strain in cooler conditions. We observed lower core body temperature, lower core temperature at sweating onset and lower perceived exertion when the participants exercised in ‘temperate’ 18°C conditions after the intervention. So if for example a non-heat-acclimated endurance athlete was performing in Rio (likely 24-28°C) we believe that taking a hot bath after exercise on 6 days (see “How to” guidelines below) would provide heat acclimation – this would in-turn reduce thermal strain during exercise and potentially improve performance, as I discuss below.

The run was approximately 1 hour. Do you expect to find similar benefits for longer events (ironman distance in hot conditions such as Hawaii?)

I see no reason why not. When heat acclimated one would expect self-selection of a higher pace during endurance exercise in the heat (as we have seen, albeit for a short 5 km run). Future studies need to confirm this. We speculated in the paper that had we used a longer running test we may have even seen an improvement in performance in ‘temperate’ 18°C conditions after the intervention: the rise in core temperature during a longer test may become a limiting factor. However, whether heat acclimation improves performance in temperate conditions is controversial, as we discuss in our paper.

Was your study performed in the Welsh winter or summer? What difference would this make?

In North Wales, with average winter temperatures of 3-9°C and summer temperatures of 13-20°C, the season makes little difference (as anyone who lives here will testify!). Although the data collection was performed year round, key is that the number of hot bath and control bath participants was the same in each season; and, none of our participants were heat acclimated; none had been exposed to hot conditions in the preceding 3 months.

How well trained were your runners? They were around 19 min for 5k? Do you expect to see benefits for athletes who are somewhat acclimated? And would these effects be seen in elite runners? Would it be seen in slower runners?

These are excellent questions. Although comparing the level of heat acclimation gained in highly trained vs. recreationally active was not our principal aim we believe our data move us some way towards an answer.

One might expect that endurance trained individuals would, by nature of having some heat acclimation at the outset, benefit less than recreationally active individuals from our hot bath intervention; viz., part of getting fit is getting hot!

It’s worth remembering that most traditional exercise-heat-acclimation studies have individuals perform daily exercise-heat-stress for a ‘fixed duration’ (e.g. 90 min) at a ‘fixed relative intensity’ in the heat (e.g. 50% of maximal oxygen uptake). In contrast, our hot bath exposure was to a large extent ‘self-regulated’ i.e. the individual removed themselves at their volition if they could not complete the 40 min.

In the published study we had 5 recreationally active individuals (2-4 h endurance exercise per week, average 5 km TT, 22 min 22 s) and 5 trained endurance individuals (>6 h endurance exercise per week, average 5 km TT, 18 min 11 s). The endurance trained demonstrated reductions in resting core temperature and exercising core temperature in the heat that were comparable to the recreationally active. Also, the endurance trained improved their 5km TT performance in the heat by 4%, on average.

That the endurance trained also benefited from the hot bath intervention is good news but of no surprise for the following reason – the endurance trained completed a longer duration in the hot bath on most days (of the max 40 min). For example, 3 of the 5 endurance trained completed the full 40 min hot bath on day 1 but only 1 of the 5 recreationally active. As such, the endurance trained actually experienced a greater stimulus for heat acclimation.

An important caveat is that we did not have a sufficient sample size to statistically compare training status in our paper; nevertheless, the preliminary results for this comparison are encouraging. We hope to have a paper with a larger sample size for the training status comparison very soon.

Are there any other potential benefits of a hot bath besides running performance?

I think the Romans can stake a claim on being the first to extol the health benefits of a hot bath! Anyone with aching bones and muscles who has bathed at a Roman spa will testify to this.

In the Bell Jar, Sylvia Plath wrote: “I am sure there are things that can’t be cured by a good bath but I can’t think of one.”

This is clearly an exciting area, ripe for investigation. Beyond the purported benefits of a hot soak to relieve aching muscles and limbs, research endeavours are focusing right now on the benefits of a hot bath for cardiovascular function, glucose regulation and immunity. As we mention in the blog, there is potential for a hot bath to benefit the injured athlete and those who struggle to perform sufficient exercise e.g. elderly or sick.

How does the magnitude of heat acclimation in your study compare with traditional heat acclimation?

The available evidence suggests very well indeed. Although we haven’t directly compared our short-term heat acclimation method with current practice; whereby, daily exercise is performed in the heat with core temperature clamped at 38.5°C, there are reasons to believe that a hot bath is a good alternative.

There are clear practical advantages i.e. no need for an environmental chamber and clamping of core temperature; a hot bath after exercise does not interfere with training or the taper ahead of competition in the heat; and, a hot bath may be incorporated into the post-exercise washing routine.

Beyond the practical advantages, we see a reduction in resting core temperature in almost all the participants we have tested with our method to date; this can be considered a ‘pre-cooling effect’. Short term (5-6 day) and even long term (10-14 day) exercise-heat-acclimation studies do not always show a reduction in resting core temperature. Clearly studies are required to compare this new method with current practice. As we discuss in the paper, and below, there is sound physiological reasoning for why our hot bath method might be favourable – combination of raised core and skin temperature.

Would sauna have a similar or better effect?

One study we discuss in our paper (by Scoon et al.) demonstrates the benefit of regular sauna bathing after exercise on exercise performance in the heat. However, that study is somewhat limited in terms of practicality and no measures of thermoregulation were made.

Are there any risks associated with the hot bath approach?

Yes, it is absolutely imperative that the individual follows the “How to” guidelines in the attached infographic.

Just like when an individual exercises in the heat it is important to listen to the cues to stop!

We know that very highly motivated individuals can ignore the cues to stop during exercise in the heat – high motivation is a risk factor for heat exhaustion, which can progress to the potentially fatal condition, heat stroke.

It is neither safe nor necessary for everyone to complete the full 40 min hot bath on each of the 6 days. In fact, as shown in Table 1 in our paper, only 4 individuals completed a 40 min hot bath on day 1.

Our guidelines allow for progression each day as the individual adapts.

Careful consideration should be given to the thermal strain in the exercise before the hot bath. Our participants only performed 40 min of moderate intensity exercise before the hot bath. They were “warm but fairly comfortable” at the end of the exercise in temperate conditions.

We recommend that the individual sits for a few minutes after getting out of the hot bath – this allows blood pressure to return to normal and limits the risk of feeling light headed.

What can you tell us about the mechanisms?

The explanation for the benefits we see of taking a hot bath after exercise require investigation but likely involve the combined elevation of core body temperature and skin temperature. As we discuss in the paper, there are studies showing that to achieve full heat acclimation it is important to have elevations in both core body temperature and skin temperature.

Reference

Zurawlew, Walsh, Fortes, Potter. Post-exercise hot water immersion induces heat acclimation and improves endurance exercise performance in the heat. Scand J Med Sci Sports DOI: 10.1111/sms.12638

Full paper can be found here on Researchgate.