Skeletal Muscle Glycogen Concentrations And Glut4 Concentrations 72 H Following Eccentric Exercise

Abstract

Muscle glycogen concentrations are significantly reduced 24-72 h after eccentric exercise that produces indices of skeletal muscle damage. It is suggested that the muscle damage produced by eccentric exercise contributes to the decrease in skeletal muscle glycogen concentrations after eccentric exercise. Decreased skeletal muscle glycogen concentrations are associated with lower GLUT4 protein concentrations 48 h after eccentric exercise. PURPOSE: To determine muscle glycogen concentrations and GLUT4 concentrations 72 h after eccentric exercise. METHODS: A total of 12 individuals performed concentric knee extensions (CON) with one leg, while the contralateral leg performed eccentric knee extensions (ECC). Subjects then cycled for 1 h at 65% of VO2peak. Muscle biopsies were obtained from the vastus lateralis of CON and ECC legs 72 h after exercise. Muscle biopsies were analyzed for muscle glycogen concentrations. Muscle damage was assessed by electron microscopy. Muscle soreness ratings were determined using a 10 point scale. Muscle biopsies were pooled and analyzed for total GLUT4 protein concentrations. RESULTS: Compared to the CON leg, muscle glycogen concentrations in the ECC leg were 25% lower 72 h after exercise (120.7 ± 8.28 vs. 157.3 ± 7.7 μmol.g wet wt-1, p < 0.05). Muscle damage such as myofibrillar disruptions and necrotic fibers were apparent in the ECC leg 72 h after exercise. Indices of muscle damage were not apparent in the CON leg. Ratings of muscle soreness in the ECC leg were higher than for the CON leg (4.43 ± 0.57 vs. 1.36 ± 0.50, p < 0.05). Total pooled GLUT4 protein concentrations were similar 72 h after exercise. CONCLUSIONS: Muscle glycogen concentrations were reduced and muscle damage was produced in the ECC leg 72 h after exercise. Pooled muscle GLUT4 protein concentrations were not altered 72 h after exercise.