Carbohydrate feeding speeds reversal of enhanced glucose uptake in muscle after exercise.

Muscle contractile activity results in an increase in glucose uptake rate that can persist for hours. This study was undertaken to determine the effect of carbohydrate repletion on reversal of an exercise-induced increase in glucose uptake. Rats were exercised by swimming. In rats studied 60 min after exercise, muscle glycogen content was 75% depleted and glucose uptake rate was increased. The effect of exercise on glucose uptake was reversed, and glycogen concentration had increased 44 mumol/g muscle, within 18 h in rats fed carbohydrate. In rats fed a carbohydrate-free diet, muscle glycogen increased only 11 mumol/g, and glucose uptake rate had returned only 50% of the way to base line 18 h after exercise. The rate of 3-methylglucose accumulation in muscles was increased sixfold 60 min after exercise. This increase in permeability to sugar was reversed within 18 h in rats fed carbohydrate. In rats fed a carbohydrate-free diet the rate of 3-methylglucose accumulation was still threefold above base line 18 h after exercise. Our results provide evidence that decreased availability of carbohydrate slows reversal of an exercise-induced increase in permeability of muscle to sugar.