Training low has received quite a bit of attention recently. It does not refer to training at low altitude, but it refers to training with low carbohydrate availability. Perhaps the most popular way is training without breakfast. However, there are many different ways to train low and these different methods also have different metabolic effects. The purpose of this blog is to give an overview of the methods available. In future blogs we will discuss the specific effects and the evidence in more detail. All of these methods may have some benefits and also have some limitations. Remember that it is not all carb, all protein or all fat! The composition of what you eat and the timing depend on the goals of the individual and the goals of individual workouts.
Low carbohydrate availability refers to a situation where the body is deprived of carbohydrate in some way. We have relatively small carbohydrate stores: 300-900 grams in the muscle and 20-90 grams in the liver. The exact amounts depend on the diet. A higher carbohydrate diet will results in greater storage. Another source of carbohydrate during exercise can be the gut (after ingesting carbohydrate). There are a number of ways to alter the stores in liver or muscle or both. Here is an overview of the methods of training low.
Low carbohydrate diet
A diet which is low in carbohydrate and more energy is coming from fat or protein (usually a combination of both). Depending on how extreme the diet is, and how hard training is, both muscle and liver glycogen will be lowered. The effects of this method are entirely depend on the severity of training and the severity of diet. Over a longer period adaptations will occur in fat metabolism, but de-adaptation may occur in carbohydrate metabolism (see my blog on the TrainingPeaks web site).
Training twice a day
Two workouts per day. The first one aims to reduce muscle glycogen. This is then followed by little or no carbohydrate intake before the second workout. This workout will then be performed with low muscle and low liver glycogen. This method has been used successfully to obtain adaptations in the muscle that favour fat metabolism. It is advised to use this method once or at most twice a week and additional recovery time may be required.
Training after an overnight fast
Training is performed before breakfast on an “empty stomach”. It is common to drink a coffee (without milk or sugar) an hour before the start of training but no calories. The workout will be performed with low liver glycogen but muscle glycogen is NOT affected. We will discuss this method in more detail in another blog. Depending on the intensity of training, additional recovery time may be needed.
Long training without carbohydrate intake
Workouts of several hours are conducted without the intake of carbohydrate intake. The start of this type of training is with normal muscle and liver glycogen stores. However as these run low and they are not being replenished with ingested carbohydrate it may be more difficult to maintain the exercise intensity. This may cause some additional stress and that stress may enhance the effects of training. Because the quality of training may be compromised, it will be a trade-off and perhaps this is a method that should be used when quality of training is not essential.
No carbohydrate during recovery
Normally it is important to consume carbohydrate for quick recovery. However, by withholding carbohydrate for an hour or a couple of hours after exercise it may be possible to get greater training adaptations. This may be at the cost of rapid recovery. (See also blog on quick recovery versus adaptations)
Recently a new methods was studied. Prof John Hawley and colleagues studied the effects of training before sleep and not consuming carbohydrate until after the workout the next morning. This method may exaggerate some of the training adaptations.
It is important to realize that there are similarities and differences between all these methods. Some methods will alter muscle glycogen stores, some only liver glycogen and some only exogenous (ingested) carbohydrates. Training quality will be affected especially if muscle glycogen is very low and a longer recovery time may be needed as well.
It is exciting to see that we now have training methods and tools that integrate training and nutrition. It means that trainer and nutritionists/dietitians have to work closely together to develop optimal nutrition strategies.
Hawley JA, Burke LM. Carbohydrate availability and training adaptation: effects on cell metabolism. Exerc Sport Sci Rev. 38(4):152-60, 2010.