In 1979 a study, which appears to be the first of its kind, showed that caffeine produced a 7% increase in the distance cycled over a 2 hour period. Since then there have been a number of other studies which have produced yet more remarkable results.
A study carried out at the University of Guelph in Ontario, Canada in 1991 showed a 44% increase in "race-pace" endurance and a 51% increase in cycling endurance, after a dosage of 9 milligrams of caffeine per kilogram of body weight.
Further studies have reported similar effects, including the study at Tufts University, Boston in 1995. It was reported that 5.5 milligrams of caffeine per kilogram of body mass produced a 29% increase in cycling endurance during high intensity circuits. The findings of this study also revealed that caffeine significantly lowers the decline in blood sugar levels.
Caffeine encourages the mobilisation of fat stores and as a result, working muscles use fat as a fuel instead of glycogen. In the first 15 minutes of caffeine induced exercise, glycogen use is decreased by anything up to 50%. Saving glycogen in the early stages of exercise results in a prolonged period of exercise due to the fact that more glycogen is available for the muscles during the latter stages of exercise.
The optimum time to take caffeine is 3-4 hours before the period of prolonged exercise. This is when caffeine becomes most effective on fat stores. To increase the effect of the caffeine, it is recommended that the athlete should decrease the level of caffeine intake in the days leading up to a period of prolonged exercise.
Although caffeine has been proven to aid endurance, anyone taking it for these purposes must consider the side effects. Some people may suffer from dehydration or in some cases, abdominal cramps and diarrhoea due to the large intestine contractions caused by the intake of caffeine.
The International Olympic Committee currently place restrictions on the level of caffeine intake. Anything above 12 mg of caffeine per litre found in urine samples will be viewed as a deliberate attempt at doping. It would take approximately 8 cups of normal strength coffee to exceed the current IOC limit. However, this can vary quite widely depending on the metabolic rate of the athlete.
