Caffeine may be the most widely used stimulant drug in the world. It is found in a variety of plants, dietary sources (tea, coffee chocolate and colas) and non-prescription medicines. The average coffee consumption in the US is approximately 2 cups of coffee per day (200 mg) while 10% of the population ingests more than 1000 mg per day. Chemically, caffeine comes from a family of compounds called trimethylxanthines. Upon ingestion, it is quickly absorbed from the stomach, reaches peak blood levels in 1-2 hours and is broken down rapidly in the liver. Caffeine has the potential to affect all systems in the body as it is absorbed by most tissues.
Scientific laboratory studies from the 1970’s suggested that caffeine enhanced endurance performance. The proposed mechanism was that caffeine increased the release of adrenaline into the blood, which in turn stimulated the release of fat from fat tissue and/or muscle. The working muscles then used this extra fat early in exercise, reducing the need to use muscle carbohydrate (glycogen). The “sparing” of muscle glycogen made more available later in exercise to delay fatigue. (This is potentially important since muscle glycogen is our main source of energy during exercise and we only have limited amount in our muscle.)
More recent studies have found that while caffeine does appear to enhance the ability to exercise for a prolonged period of time, the “glycogen sparing” mechanism explained previously does not always occur. The most recent work in this area reported that the ingestion of 3-9 mg of caffeine per kilogram of body weight one hour prior to exercise increased endurance running and cycling performance. To put this in perspective, 3 mg per kg body wt. of caffeine equals approximately 1 mug or 2 regular size cups of drip-percolated coffee. Thus, while the mechanism of action of caffeine is unclear, its ability to enhance endurance exercise performance by up to 30% is well established, although caffeine is no longer a “controlled or restricted substance” as defined by the International Olympic Committee (IOC). Until recently, athletes were allowed up to 12 ug caffeine per milliliter of urine before it was considered illegal.
While research has demonstrated that “pure” caffeine will enhance endurance exercise, does the ingestion of similar amounts of caffeine taken in the form of coffee have the same effect? A study done by Dr. Terry Graham at the University of Guelph, Ontario, Canada and published in the Journal of Applied Physiology investigated whether caffeine in the form of coffee would enhance performance to the same degree as pure caffeine. Nine, highly trained endurance athletes underwent five separate trials. The athletes were asked to run on a treadmill to exhaustion after ingesting a placebo pill, caffeinated coffee, decaffeinated coffee, decaffeinated coffee with the caffeine added back into it, and pure caffeine. The trials were separated by about 1 week and the treadmill was adjusted to the same speed and grade for each trial. The caffeinated trials contained the same amount of caffeine (i.e. the caffeinated coffee and the decaffeinated coffee with the caffeine added back in had the same amount of caffeine as the pure caffeine pill). Surprisingly, the only trial which resulted in any improvement in performance was when subjects ingested pure caffeine. In other words, ingesting caffeine in the form of coffee did not affect performance compared to the placebo trial. Thus, it was concluded that there is a compound in coffee that appears to inhibit the performance enhancing effects of caffeine and to obtain the performance enhancing effects of this drug, pure caffeine needs to be ingested.
An equally important issue is the use of caffeine by the average active teenager. Caffeine’s widespread use was demonstrated by a recent survey that reported approximately 27% of youths (11-18 yrs old) had used a caffeine-containing substance for the specific purpose of enhancing performance. Could this seemingly “safe” practice lead to the use of more dangerous substances? For the average, active teenager or adult who is exercising with the goals of enjoyment and self-improvement, using caffeine defeats these purposes. Proper training and adequate nutritional habits are more sensible and productive approaches.
Another interesting and relatively new finding about caffeine is its potential to increase insulin resistance (a condition that can lead to type II diabetes). Scientific studies have found that caffeine decreases glucose uptake in skeletal muscle and that the body requires more insulin to handle glucose when caffeine and/or coffee have been ingested. Obviously this may have some serious consequences for individuals who are insulin resistant or who have either type I or type II diabetes.
How does all of this relate to cycling? Well, there are definite performance enhancing effects to be had by ingesting pure caffeine. Some researchers have suggested that it should be a substance that is completely banned, however, this is highly unlikely since it is so common in our regular diet. In fact, caffeine ingestion has been compared to carbohydrate loading in terms of its ethical consideration. Whether one takes caffeine for the specific purpose of trying to enhance performance is up to the individual. It is definitely one of the safer “doping” techniques out there.