Abstract

Endurance capacity of human vastus lateralis muscles was observed 24 h after hard exercise followed by either a carbohydrate-restricted or a carbohydrate-loaded diet (depletion and repletion). In a control condition the subjects did no previous exercise and ate their normal diet. Each of these conditions was followed by an experimental protocol in which the 5 male subjects made a series of alternating 25-s static contractions of each leg at 50 MVC until one leg failed to achieve the required force (Tlim). Glycogen concentration before the experimental protocol in both legs was significantly lower in the depletion than in the repletion condition. Muscle lactate and creatine phoshate concentrations were within normal limits before the static contractions. The number of contractions the repleted and depleted legs could sustain before Tlim were not different from each other, but both were 35 fewer than the control. Surface EMG amplitude was higher in depleted than in repleted or control muscles. At Tlim, EMG amplitude was maximal, creatine phosphate was 50-70 depleted, and lactate increased fourfold. Average glycogen utilization per contraction in both the repletion and depletion conditions was 5.8 mmol/kg dry wt, but postexercise lactate concentrations were lower in depleted than in repleted muscles. The EMG frequency distribution shifted downward in all conditions during the experimental protocol and was independent of muscle lactate concentration. Verf.-Referat (gekuerzt)