Supercompensation of muscle glycogen in trained and untrained subjects

The purpose of this study was to determine whether or not trained athletes have the same capacity for supercompensation of muscle glycogen as untrained subjects. Muscle glycogen was measured in 4 highly trained cyclists and 4 untrained controls over a 6 day period of exercise and dietary manipulation. During the week prior to the investigation the trained group tapered their training load but maintained a high carbohydrate intake as they would in preparation for a major competition. Needle biopsies were taken from the vastus lateralis before and after exhaustive cycle ergometry at 73% VO2 max followed by several sprint intervals, after 3 days on a carbohydrate-restricted diet and after 2 and 3 days on a high carbohydrate diet. All food intake was quantified and plasma insulin and glucose were monitored daily. The mean initial glycogen concentration for the trained group was 115 mmol X kg-1 wet muscle weight and 92 mmol X kg-1 for the untrained group. Both groups showed similar post exercise depletion and recovery patterns when expressed as a % of their initial values. Following 3 days of high carbohydrate diet, the glycogen concentration for the trained cyclists reached 174 mmol X kg-1 or 152% of its initial value while the untrained-group reached 143 mmol X kg-1 or 155% of its initial value. It was concluded that a regimen of exhaustive exercise, followed by a period of carbohydrate restriction and a period of high carbohydrate intake, results in substantially higher muscle glycogen storage than can be achieved by a reduction in training in combination with high carbohydrate intake.(ABSTRACT TRUNCATED AT 250 WORDS)