Effect Of Training Intensity On Skeletal Muscle And Liver Glycogen In Rat

Abstract

PURPOSE: It has been shown that endurance-trained rats have higher muscle and liver glycogen content than sedentary controls. Whether glycogen content is affected differently by training intensity, however, is undetermined. Therefore, the effects of chronic treadmill exercise at low, moderate, and hard intensity on liver and skeletal muscle glycogen content was investigated. METHODS: Forty male Wistar rats were assigned to control, low (18 m/min), moderate (26 m/min), and high (34 m/min) intensity groups. Training groups underwent treadmill exercise (60 min/day, 5 days/week) for 12 weeks. Liver and gastrocnemius muscle were removed and glycogen content was assessed by colorimetric method. Data was analyzed by ANOVA and significance was P≤0.05. RESULTS: Regardless of exercise intensity, trained groups had significantly higher liver but lower muscle glycogen content compared to controls. However, the high compared to the low and moderate intensity groups possessed significantly lower muscle glycogen levels. CONCLUSIONS: These results indicate that 12 weeks of low, moderate, and hard intensity exercise resulted in elevated liver glycogen but depleted muscle glycogen levels. The greater muscle glycogen depletion after high intensity training may be due to tissue damage. It appears that 12 weeks of treadmill exercise resulted in liver not muscle glycogen compensation in Wistar rats.