SKELETAL-MUSCLE GLUT-4 AND POSTEXERCISE MUSCLE GLYCOGEN-STORAGE IN HUMANS

The purpose of this study was to examine the relationship between skel etal muscle GLUT-4 protein and postexercise glycogen storage in human subjects fed adequate carbohydrate. Eleven men completed 2 h of cyclin g, and a biopsy of the vastus lateralis was performed immediately afte r exercise cessation for the determination of muscle GLUT-4 protein an d glycogen concentrations, glycogen synthase activity, and citrate syn thase activity. The subjects ingested meals providing 2.0 g carbohydra te/kg body weight at 0, 2, and 4 h postexercise, and a second biopsy w as performed 6 h postexercise. Muscle glycogen concentration increased significantly during the 6-h recovery period (glycogen immediately po stexercise, 27.2 +/- 5.4 mmol/kg wet weight; glycogen storage, 52.4 +/ - 2.9 mmol . kg wet weight(-1). 6 h(-1); P < 0.05). Glycogen storage d uring recovery was directly related to GLUT-4 protein (2.20 +/- 0.33 a rbitrary standard units; r = 0.63; P < 0.05) and inversely related to glycogen immediately postexercise (r = -0.70; P < 0.05). A direct corr elation existed between glycogen storage during recovery and the activ ity of the I form of glycogen synthase (r = 0.60; P < 0.05). These res ults suggest that muscle GLUT-4 protein concentration, as well as fact ors relating to glucose disposal, may affect postexercise glycogen sto rage in humans fed adequate carbohydrate.