What’s the deal with caffeine? Does it truly improve race times and help with training? If it does improve performance can we dose up on caffeine and not have any worries about getting caught? Is it a banned substance? Are there any major side effects with taking large amounts of caffeine?
Written by Tim Mickleborough
Caffeine has proven ergogenic effects, and its use in competition is legal as long as concentrations in the urine do not exceed a predetermined limit. Caffeine should not be considered synonymous with coffee. Caffeine is only one of more than 100 chemicals found in coffee, which is only 2 percent caffeine. Caffeine is found in many beverages, such as soft drinks (e.g., Surge, Mountain Dew) and “energy” drinks (e.g. Red Bull). Other sources of caffeine include teas and over-the-counter headache and anti-drowsiness remedies.
Despite decades of research, exercise scientists and sports medicine professionals are still uncertain of some of caffeine’s effects. We still lack good dose-response data for caffeine, and there has been a failure to distinguish between acute effects (caffeine’s effects in those who do not normally use it) from chronic effects. Caffeine’s effect on heart rate may depend on when it is ingested. Generally, caffeine increases resting heart rate in caffeine non-users. One study has found that neither resting nor exercise heart rates were affected by a large (10 mg/kg), single dose of caffeine in caffeine-naive recreational cyclists who cycled to exhaustion (1). However, other studies have found increases in heart rates during exercise following caffeine ingestion. It appears the timing of measurements and the type of subject may influence how investigators interpret caffeine’s effect on heart rate.
Caffeine is known to exert a moderate diuresis (i.e. dehydrating effect). However, while research suggests that while ingesting caffeine at rest does induce a diuretic response, ingesting caffeine during exercise does not (2). Acutely, caffeine can increase the basal metabolic rate and enhance fat oxidation during exercise. It has been shown that plasma levels of free fatty acids increase 50-100 percent following caffeine ingestion. Thus, the increased availability of free fatty acids may lead to a glycogen-sparing effect and thereby delay fatigue.
Since both caffeine and theophylline are xanthines, it is not surprising that caffeine exerts some actions similar to those of theophylline. For example, both xanthines exert protective effects in exercise-induced asthma (3). Caffeine has been found to increase vigilance and decrease motor reaction time in response to both auditory and visual stimuli. However, caffeine may be detrimental in tasks requiring fine-motor coordination.
The general consensus of research findings is that caffeine improves continuous exercise time to exhaustion. This effect appears to increase as the duration of the event exceeds 30 minutes, but caffeine has also been shown to enhance performance during incremental exercise protocols lasting eight to 22 minutes and sprints lasting less than 90 seconds (4).
Athletes may experience unpleasant side effects while taking caffeine, such as nausea and abdominal discomfort, particularly when ingesting 400-500 mg caffeine or more. Another drawback to routinely using caffeine is a withdrawal syndrome can occur after cessation of regular use.
- Increases aerobic endurance secondary to glycogen-sparing effect
- Improves voluntary reaction time
- Enhances alertness
- May prevent exercise-induced asthma
- Causes tremors and decreases hand steadiness
- May cause tolerance and withdrawal symptoms
- Intake cannot exceed acceptable urinary levels in NCAA- and USOC-sanctioned competition
- Has a diuretic effect if consumed several hours prior to exercise
According to the NCAA and USOC, caffeine is officially classified as a restricted substance and not a banned substance. Single doses of caffeine at 9 mg/kg or greater produce urine concentrations that exceed the USOC/IOC’s and NCAA’s acceptable limits, which are 12 mgc/ml (60μmol/l) and 15 mgc/ml respectively. It is important to note doses of 3-6 mg/kg, which do not produce urine concentrations that would result in disqualification, have been found to be ergogenic (5). To put these dosages into some perspective, consider the following: one cup of regular coffee contains 100 mg of caffeine and a can of Red Bull contains 115 mg of caffeine, while the equivalence in urine within two to three hours is 1.50 mgc/mL and 1.73 mgc/mL respectively.
If you choose to use caffeine as an ergogenic aid, avoid routine use. Individuals build a tolerance to many of the effects of caffeine within days. In addition, caffeine has diuretic actions and has detrimental effects on hand steadiness and possibly reaction time. As to the ethics of using caffeine to enhance performance, the IOC stipulates that taking any physiologic substance in abnormal quantity with the intention of artificially and unfairly increasing performance should be construed as doping.
1. Flinn S, Gregory, J, McNaughton L R, Tristram, S. and Davies, P. (1990). Caffeine ingestion prior to incremental cycling to exhaustion in recreational cyclists. International Journal of Sports Medicine, 11: 188-193.
2. Wemple R D, Lamb D R. and Mckeever, K H. (1997). Caffeine
vs. caffeine-free sports drinks: Effects on urine production at rest during prolonged exercise. International Journal of Sports Medicine, 18: 40-146. 3. Kivity S, Ben Aharon Y, Man A. and Topilsky M. (1990). The effect of caffeine on exercise-induced bronchoconstriction. Chest, 97: 1083-1085.
4. Armstrong L E, Casa D J, Maresh C M. and Ganio M S. (2007). Caffeine, fluid-electrolyte balance, temperature regulation, and exercise-heat tolerance. Exercise and Sport Sciences Reviews, 35: 135-140.
5. Pasman W J, van Baak M A, Jeukendrup A E. and de Haan A. (1995). The effect of different dosages of caffeine on endurance performance time. International Journal of Sports Medicine, 16: 225-230.