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 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.
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.
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.
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