Caffeine

Caffeine, one of several mehylxanthines found in coffee, tea, cola, chocolate, and a variety of other foods and beverages, has been shown to help endurance-type performance in people who are unaccustomed to consuming caffeinated products.³⁸ Caffeine is a central nervous system stimulant and a muscle relaxant. It has recently been removed from the IOC's banned substance list. In a number of studies, caffeine ingestion significantly increased free fatty acid (FFA) concentration in plasma.³⁹ The increased availability of FFAs enhances the ability of cells to usethese fats as a fuel in endurance-type, low-intensity activities. Since humans adapt to caffeine intake, frequent and regular consumption results in a reduced dose effect. Put simply, the more you consume, the more you need to consume to achieve the same ergogenic effect. Overconsumption of caffeine is associated with irritability, insomnia, diarrhea, and anxiety. In addition, a large volume of caffeine intake may induce a diuresis that could exacerbate the state of dehydration.

Caffeine consumed at doses of between 3 and 9 milligrams per kilogram or a total of approximately 250 milligrams appears to aid performance in long-endurance activity and may also improve performance in more intense short-duration exercise.^38,40 It remains unclear as to why caffeine has this apparent ergogenic benefit, although it has been hypothesized that it may stimulate the sympathetic nervous system and enhance utilization of fatty acids, thereby sparing limited glycogen stores.^41,42 A central nervous system stimulant, caffeine may stimulate the brain into a lower level of fatigue to allow a continuation of performance at a higher level. Now that the IOC no longer bans caffeine, it is likely that athletes will incorporate caffeine into a more regular and higher usage pattern. Except for the dependence problem it creates with regular use (discontinuation produces irritability, headache, and mood shifts), it is a relatively safe substance to consume.⁴³