Bushwacka: Thank You. I don't think I have ever heard of positives for soft drinks during exercise.
Caffeine and Athletic Performance:
Despite considerable research in this area, the role of caffeine as a performance enhancing drug is still controversial. Some of the data are conflicting, which is in part due to how the experimental studies were designed and what methods were used. However, there is general agreement in a few areas:- Caffeine does not appear to benefit short term, high intensity exercise (eg. sprinting)
- Caffeine can enhance performance in endurance sports.
Glycogen is the principal fuel for muscles and exhaustion occurs when it is depleted. A secondary fuel, which is much more abundant, is fat. As long as there is still glycogen available, working muscles can utilize fat. Caffeine mobilizes fat stores and encourages working muscles to use fat as a fuel. This delays the depletion of muscle glycogen and allows for a prolongation of exercise. The critical time period in glycogen sparing appears to occur during the first 15 minutes of exercise, where caffeine has been shown to decrease glycogen utilization by as much as 50%. Glycogen saved at the beginning is thus available during the later stages of exercise. Although the exact method by which caffeine does this is still unclear, caffeine caused sparing in all of the human studies where muscle glycogen levels were measured. The effect on performance, which was observed in most experimental studies, was that subjects were able to exercise longer until exhaustion occurred.
In addition to the beneficial effects on muscle, caffeine may alter the perception of how hard you are working. During testing, athletes are asked to judge their effort, which is referred to as the rating of perceived exertion (RPE). Some studies have yielded significantly lower RPE's -- less fatigue -- when the athlete used caffeine. Other studies have not found this effect. Obviously, the RPE is very subjective, and there are many things that may influence it.
What about Caffeine in Ironman races?The exercise studies on caffeine involved endurance testing of approximately 2 hours, so there is no specific information related to ultra-endurance races. Pre-race caffeine may be beneficial though, because the longer the race, the more important fat is as a fuel. During the race, caffeinated soft drinks are one of the choices at the aid stations in an Ironman. Whether this source of caffeine is useful is unknown, but these soft-drinks do supply necessary carbohydrate. Because longer races have a greater baseline risk of dehydration, nausea and abdominal cramps, it is very important to consider the side effects of caffeine (below)Variable results and side effects!Despite the known benefits of caffeine in endurance exercise, individual results may vary greatly. Differences in metabolism, diet, and frequency of caffeine use are some of the factors that can determine how an individual will react to caffeine. Additionally, some athletes may actually experience a decrease in performance, usually due to side effects of caffeine.
Although caffeine does not appear to significantly alter water balance or body temperature during exercise, dehydration is a potential concern because caffeine is a mild diuretic. Some athletes may also experience abdominal cramps and diarrhea related to the large intestine contractions caused by caffeine. The combination of dehydration and cramping can have particularly detrimental effects on performance.
« Last Edit: July 12, 2011, 01:36:53 pm by jim-ratliff »
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