Caffeine and Exercising

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fittiephd
fittiephd Posts: 608 Member
in Fitness and Exercise
http://www.rice.edu/~jenky/sports/caffeine.html


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%.


The interesting part for me was that it seems that caffeine before working out makes you burn fat before you burn carbs... interesting idea.

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  • tigersword
    tigersword Posts: 8,059 Member
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    It's not so much that you burn fat before carbs, but that you need carbs in order to burn fat. Fat is very inefficient as an energy source, and on its own, fat burning can't keep up with high intensity exercise. By burning glycogen with the fat, the body can utilize fat as it becomes available, with glycogen filling in the gaps. Basically caffeine helps speed up the fat burning part, so the gaps where glycogen is needed are shortened, which helps extend the glycogen supply.

    The inefficiency of fat as a sole energy source is also part of the reason that endurance exercise leads to muscle catabolism, as the protein from the muscle can be burned with the fat to increase efficiency and maintain a constant energy source, as gluconeogenesis can use the protein and fat to make more glycogen.

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