Representatives at the American College of Sports Medicine couldn't find any studies on the athletic performance of twin athletes who are members of a male-female set.

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For example, in 1995, the American College of Sports Medicine and the Centers for Disease Control and Prevention jointly issued national guidelines called Physical Activity and Public Health, which were updated in 2007.

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The Indirect calorimetry is well established and widely used to measure metabolism, and recommended for the treatment of obesity and management of weight by World Health Organization, American Dietetic Association and American College of Sports Medicine.

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The American College of Sports Medicine recommends that endurance and strength training athletes consume higher levels of daily protein than the standard recommended daily allowance (i.e. 1.2-1.7 grams of protein for each kilogram of body weight, versus 0.8 grams per kilogram per day).

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Tony Ordas, a San Diego personal trainer and exercise specialist for the American College of Sports Medicine, says many surfers make the mistake of only working what Mr. Ordas calls their "mirror muscles, " those that get shown off when wearing a swimsuit, such as the abs and biceps.

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