EFFECTS OF ECCENTRIC AND CONCENTRIC EXERCISE ON MUSCLE GLYCOGEN REPLENISHMENT

Eccentric contractions appear to reduce muscle glycogen replenishment during the 1- to 10-day period after exercise. The main purpose of this study was to determine whether consuming a large amount of carbohydrate (1.6 g.kg-1.h-1) during the 4 h after glycogen-reducing exercise would produce different patterns of glycogen replenishment in human muscle that had undergone either eccentric or concentric contractions approximately 2 or 48 h earlier. Subjects cycled for 75 min and undertook interval exercise to deplete glycogen on days 1 and 3. After cycling exercise on day 1 only, subjects performed 10 sets of 10 repetitions of either concentric or eccentric contractions in opposite legs. During the 4 h after exercise, subjects consumed 0.4 g carbohydrate/kg body wt every 15 min. Biopsies were obtained immediately before the feedings and 4 h later, and blood was sampled every 15 min. For days 1 and 3 combined, total integrated areas for the glucose and insulin response curves averaged 1,683 mumol.ml-1.240 min-1 and 21,450 muU.ml-1.240 min-1, respectively. For days 1 and 3 combined, muscle glycogen replenishment after concentric exercise averaged 10 mmol.kg-1.h-1. On day 1 glycogen replenishment was similar for subjects performing either concentric or eccentric contractions. On day 3, however, glycogen replenishment was 25% lower (P < 0.05) in muscle that had undertaken eccentric contractions 48 h earlier than in concentrically exercised muscle. In conclusion, glycogen replenishment can be stimulated to a high rate when a large amount of carbohydrate is consumed after glycogen-depleting concentric exercise. Furthermore, such a carbohydrate feeding regimen does not produce comparable glycogen replenishment in muscle that 48 h earlier has undergone eccentric rather than concentric contractions.