Muscle glycogen repletion after high-intensity intermittent exercise

Six subjects exercised to exhaustion on a cycle ergometer at intensities corresponding to approximately 140% of their maximal aerobic power. Subjects attempted to pedal for 1-min intervals with 3-min rest periods between, and continued until 30 s of exercise could no longer be maintained. Venous blood was sampled for lactate and glucose analysis. Muscle biopsies were extracted from the quadriceps before and immediately after exercise and at 2-, 5-, 12-, and 24-h intervals thereafter for total glycogen analysis. Three subjects consumed a mixed controlled diet (approx. 3,100 kcal) during the 24 h after exercise, and three consumed the same diet plus an additional 2,500/kcal carbohydrate. Following exercise, glycogen concentration had dropped to a mean value of approximately 28% of its preexercise value. After 2 h, it had recovered to 39%, at 5 h to 53%, at 12 h to 67%, and at 24 h to 102% of its preexercise value, with no difference in resynthesis rate between the two groups. It was concluded that, following glycogen depletion through intense intermittent exercise, complete recovery to preexercise values may be accomplished within 24 h; and that within this time period, the rate of resynthesis cannot be accelerated by a higher than normal carbohydrate intake.