Caffeine Effects on Sporting Performance – Part 1: Metabolism Studies

With the World Cup in Brazil capturing the eyes of the world and the start of the Tour de France this week (unusually, this year’s famous French cycle race begins in Yorkshire, England), SelectScience is looking at the slightly controversial performance-enhancing effects of caffeine.

Sportomics experiment
Despite considerable research in this area, the role of caffeine as a performance-enhancing drug is still controversial. There is general agreement from research that caffeine does not appear to benefit short-term, high intensity exercise (e.g. sprinting) but that caffeine can enhance performance in endurance sports. We were keen to determine how caffeine affects footballers playing in Brazil through our Sportomics analysis experiment (see Professor Cameron of the Federal University of the State of Rio de Janeiro discuss caffeine and player performance), and have compared this to recent research on stage based endurance events such as the Tour de France.

Dr Kevin Currell, RNutr (Sports & Exercise) from the English Institute of Sport commented to SelectScience: “The research would suggest there is a positive effect on performance using caffeine, across a variety of events. However, this needs to be balanced by such things as sleep quality if caffeine is taken too late in the day. Dosing is also important, as too much can be a bad thing.”

Caffeine metabolism
Despite a great deal of research, it is still unclear how caffeine is metabolized in the body. Glycogen is the principal fuel for muscles and exhaustion occurs when it is depleted. A secondary fuel, which is much more abundant, is fat. As long as there is still glycogen available, working muscles can utilize fat. Caffeine mobilizes fat stores and encourages working muscles to use fat as a fuel. This delays the depletion of muscle glycogen and allows for a prolongation of exercise. The critical time period in glycogen sparing appears to occur during the first 15 minutes of exercise, where caffeine has been shown to decrease glycogen utilization by as much as 50%. Glycogen saved at the beginning is thus available during the later stages of exercise.

One possible mechanism of action for the effect of caffeine and delaying the onset of fatigue is the competition of caffeine with adenosine for receptor binding. Adenosine is a biochemical molecule that has inhibitory effects on the central nervous system. As adenosine binds to receptors, prevalence of fatigue increases, and arousal decreases. Caffeine binding to these receptors prevents adenosine binding, thus increasing arousal and decreasing fatigue. Caffeine also increases calcium permeability in sarcoplasmic reticulum and increases the sensitivity of the myofibrillar proteins to calcium by inhibiting the accumulation of cyclic AMP. These effects of caffeine enhance exercise and athletic performance, by enabling the athlete to exercise longer until exhaustion occurs.

In part 2, we look at the variable results from caffeine studies, the benefits, side effects and technologies (including mass spectrometry and capillary electrophoresis) used in the analysis of caffeine in sports drinks and athlete performance.

Image Credit:My Organic Chemistry