Answered by Ingrid Ducmanis on Monday, June 1, 2009
You figure that if a double latte can keep you alert at meetings, it can certainly enhance your workout. According to the American College of Sports Medicine (ACSM), having caffeine before exercise increases performance during prolonged endurance exercise and short-term intense exercise lasting approximately five minutes. A dose of three to nine milligrams (mg) of caffeine per kilogram of body weight (that's an average range of two to six cups of coffee) one hour prior to working out should do the trick. Caffeine has been shown to help release stored body fat so that it can be used as energy, explains Jack L. Smith, Ph.D., chair of the department of nutrition at the University of Delaware. But caffeine also acts as a diuretic, warns Smith, speeding urine production and dehydration, which robs your body of the water it needs for cooling. (The ACSM maintains that this immediate diuretic effect has yet to be conclusively supported by research.) Research suggests that the caffeine effect works best for those who are not regular caffeine drinkers. Doses of around 200 mg—a little more than a cup of coffee or 48 ounces of cola—have proven to boost performance, while doses above 400 mg may have the opposite effect.