Caffeine and Exercise Performance
James Meschino DC, MS, ROHP
Caffeine stimulates the release of fatty acids from fat cells by increasing the activity of hormone sensitive lipase, which hydrolyzes triglycerides within fat cells to free fatty acids and glycerol, enabling them to diffuse into the blood stream. Once in the blood stream free fatty acids can be taken up by the exercising muscle and used as a source of fuel to generate ATP. Studies show that consuming 330 mg of caffeine ingested 60 minutes prior to an endurance event, can increase endurance performance (in the range of 75 – 80% VO2 max), and spare glycogen depletion within the working muscles, further enhancing the length of time the muscle can perform at more optimal power during sub-maximal, endurance events. Caffeine has been shown to inhibit the enzyme phosphodiesterase (which degrades cAMP), thereby elevating cAMP levels within fat cells and other cells. Within fat cells, higher cAMP stimulates activity of hormone sensitive lipase, which in turn, releases free fatty acids and glycerol to the bloodstream. Caffeine also increases blood levels of catecholamines, such as epinephrine and nor epinephrine, which act as stimulants of the nervous system and promote mobilization of fat stores.
A review of the literature indicates that caffeine intake at 6 mg per kg of body weight enhances endurance performance, and this level of intake would result in urinary caffeine concentrations below the current International Olympic Committee (IOC) restricted level of 12 mg/L, and thus, consideration should be given to lowering this level.
Most studies have found that caffeine intake does not enhance performance of short duration, high intensity exercise (e.g., sprints, weight lifting), although some evidence does support this application as well. Health professionals should note that caffeine is banned by the IOC at urinary levels of 12 mg/L or higher, which would require an intake of several cups of coffee over a short period to reach the lowest threshold of restriction. A typical cup of coffee contains approximately 250 mg of caffeine.
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