Function of Dietary Carbohydrate

Although stored fat can provide significant energy for prolonged and/or moderate-intensity exercise, it is well established that carbohydrate is the major muscle fuel­particularly when exercise is intense such as would occur with strength training. The underlying reason relates to the maximal rate at which energy for muscle contraction (adenosine triphosphate [ATP]) can be regenerated. Oxidative energy delivery takes several minutes to be fully used and has a maximal ATP delivery rate of about 2.5 mmol/kg drymatter/sec. This is much less than anaerobic energy delivery that is instantaneous and can deliver in excess of 11 mmol/kg dry matter/sec. During situations in which carbohydrate stores are depleted, i.e., starvation and/or prolonged exercise, body protein can be mobilized to help meet the energy need 15 and/or to optimize aerobic energy production by increasing the concentration of tricarboxylic acid cycle intermediates via the alanine aminotransferase reaction (anaplerotic role) . Both situations would be disadvantageous for strength athletes as they would lead to decreases in muscle mass and strength. As a result, carbohydrate intake is critical for strength athletes and daily intake should be at least 5-6 g/kg-for some, even higher.