Glycogen resynthesis in human muscle fibre types following exercise‐induced glycogen depletion.

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Abstract
1. Studies investigating muscle glycogen resynthesis in man have usually examined mixed‐fibred biopsies or have used histochemical methods to estimate single fibre resynthesis. Since the accuracy of the latter is open to debate, this study investigated glycogen resynthesis in type I and II fibres using biochemical methods of analysis. 2. Seven subjects performed one‐legged cycling exercise to exhaustion. During the initial 2 h of recovery, subjects consumed 3 g of glucose (kg body mass (BM))‐1, and a high carbohydrate diet thereafter. Muscle biopsy samples were obtained from both legs at exhaustion, and from the exercised leg after 3, 10 and 24 h of recovery. 3. In the initial 3 h of recovery, there was a 25 +/‐ 8% higher rate of resynthesis in type I compared with type II fibres (41 +/‐ 3 and 31 +/‐ 4 mmol glucosyl units (kg dry mass (DM))‐1 h‐1, respectively; P < 0.05). Between 3 and 10 h of recovery, resynthesis in type I fibres declined by 60 +/‐ 13% to 15 +/‐ 4 mmol glucosyl units (kg DM)‐1 h‐1 (P < 0.01), whilst the rate in type II fibres was maintained. Good agreement was found when relating the mixed‐fibred muscle glycogen concentration to the mean concentration found in type I and type II fibres (r = 0.96). 4. A discrepancy was found to exist with histochemically derived data reported in the literature. The higher initial glycogen resynthesis rate in type I fibres may be attributable to fibre‐type differences in glucose uptake and disposal.(ABSTRACT TRUNCATED AT 250 WORDS)