Abstract

The primary purpose of this study was to determine whether gastric emptying limits the rate of muscle glycogen storage during the initial 4 h after exercise when a carbohydrate supplement is provided. A secondary purpose was to determine whether liquid (L) and solid (S) carbohydrate (CHO) feedings result in different rates of muscle glycogen storage after exercise. Eight subjects cycled for 2 h on three separate occasions to deplete their muscle glygogen stores. After each exercise bout they received 3 g CHO/kg body wt in L (50 glucose polymer) or S (rice/banana cake) from or by intravenous infusion (I; 20 sterile glucose). The L and S supplements were divided into two equal doses and administered immediately after and 120 min after exercise, whereas the I supplement was administered continuously during the first 235 min of the 240-min recovery period. Blood samples were drawn from an antecubital vein before exercise, during exercise, and throughout recovery. Muscle biopsies were taken from the vastus lateralis immediately after and 120 and 240 min after exercise. Blood glucose and insulin declined during exercise and increased significantly above preexercise levels during recovery in all treatments. The increase in blood glucose during the I treatment, however, was three times greater than during the L or S treatments. The average insulin response of the L treatment was significantly greater than that of the S treatment but not that of the I treatment. Despite the differences in the blood glucose and insulin responses, no differences in muscle glycogen storage rates were found between treatments during the first or second 2 h of recovery. It was concluded that the rate of muscle glygogen storage after exercise is similar when 3 g CHO/kg body wt is administered in L or S form and that the rate of storage under these conditions is not limited by the gastric emptying rate of the supplement. Verf.-Referat