NUTRITION AND HEALTH
Caffeine - What does caffeine do? - What events can benefit from taking Caffeine?
Various elements are explored, from nutritional requirements to boost energy levels to the pros and cons of caffeine.
An ABC of nutritional ergogenic aids and dietary supplements.
Caffeine occupies an unusual position in sports nutrition. It is a drug that is capable of enhancing performance in a variety of different sports, but the doping regulations of the International Olympic Committee recognise that it is also a part of the normal diet for most people in the world. Because of this, athletes are allowed to take caffeine up to a certain level, and the permitted level is sufficient to give a performance advantage.
Caffeine affects a number of different tissues in the body, including the muscles, the brain and the fat cells. Early studies on the use of caffeine concentrated on its effects on endurance events, where it can act to increase the supply of fat available to the working muscles, thus sparing the limited carbohydrate (glycogen) stores and delaying the point of fatigue. For this reason, caffeine use was popular with marathon runners in the 1980's, but it seems to be less widely used today. This is probably one of the main actions in endurance events, but caffeine can also affect the brain, decreasing the subjective feelings of effort and increasing fatigue resistance.
Caffeine is present in many foods, but is a "controlled or restricted drug". Urine levels greater than 12 mg/l are considered illegal by the IOC. Caffeine is not tested out of competition.
It has been known for a long time that caffeine can increase strength in muscles, and it does so by altering the way in which the muscle deals with calcium, which is an essential part of the force-generating process. It is only recently, however, that it has been shown that taking caffeine before short duration high intensity exercise, equivalent to running 1500 metres, can improve performance. Here the effect is certainly not to increase fat use by the muscle, as this would not give a better performance.
Caffeine is a mild stimulant that can increase alertness and help fight off drowsiness. This is the reason for its inclusion in many herbal stimulant preparations. A high dose may have unwanted effects, making you feel jittery and it may prevent sleep.
What events can benefit from taking Caffeine?
It is not entirely clear what events will benefit most from taking caffeine, but laboratory studies have shown improvements in performance in events lasting from a few minutes to 2 hours or more. This covers the full range of events from 1500 m to the marathon. Although caffeine has traditionally been used mostly by endurance athletes, including marathon runners and cyclists participating in multi-stage events such as the Tour de France, it seems that there may be benefits for athletes competing in shorter track events.
Some experiments show improvements in strength, and it might be expected that this would translate into improvements in sprinting speed, but the experiments to prove this seem not to have been done.
Caffeine could be used in training with the aim of increasing fat use and possibly increasing the effectiveness of training sessions. There is little or no evidence to support this at present and the scope for caffeine use seems to relate to acute use in competition.
Caffeine ingestion 1-3 hours before exercise can improve performance in events lasting from a few minutes to several hours.
Caffeine can also increase force generating capacity (strength) in isolated muscles stimulates to contract
It seems likely that different mechanisms of action are involved.