TIME COURSE OF GLYCOGEN ACCUMULATION AFTER ECCENTRIC EXERCISE

This study examined the time course of glycogen accumulation in skeletal muscle depleted by concentric work and subsequently subjected to eccentric exercise. Eight men exercised to exhaustion on a cycle ergometer [70% of maximal O2 consumption (VO2max)] and were placed on a carbohydrate-restricted diet. Approximately 12 h later they exercised one leg to subjective failure by repeated eccentric action of the knee extensors against a resistance equal to 120% of their one-repetition maximum concentric knee extension force (ECC leg). The contralateral leg was not exercised and served as a control (CON leg). During the 72-h recovery period, subjects consumed 7 g carbohydrate.kg body wt-1.day-1. Moderate soreness was experienced in the ECC leg 24-72 h after eccentric exercise. Muscle biopsies from the vastus lateralis of the ECC and CON legs revealed similar glycogen levels immediately after eccentric exercise (40.2 +/- 5.2 and 47.6 +/- 6.4 mmol/kg wet wt, respectively; P > 0.05). There was no difference in the glycogen content of ECC and CON legs after 6 h of recovery (77.7 +/- 7.9 and 85.1 +/-4.9 mmol/kg wet wt, respectively; P > 0.05), but 18 h later, the ECC leg contained 15% less glycogen than the CON leg (90.2 +/-8.2 vs. 105.8 +/- 8.9 mmol/kg wet wt; P < 0.05). After 72 h of recovery, this difference had increased to 24% (115.8 +/- 8.0 vs. 153.0 +/- 12.2 mmol/kg wet wt; P < 0.05). These data confirm that glycogen accumulation is impaired in eccentrically exercised muscle. However, impairment is a delayed response, inasmuch as the rate of accumulation was normal in the eccentrically exercised muscle for the initial 6 h of recovery.