Changes in insulin action and GLUT-4 with 6 days of inactivity in endurance runners

240-244, 1996.-The purpose of this investigation was to determine whether decreased insulin action after 6 days of inactivity in endurance-trained runners was associated with a decrease in skeletal muscle glucose transporter protein levels (GLUT-4) in the gastrocnemius muscle. Seven endur-ance runners (5 men and 2 women) volunteered to participate in this investigation. All subjects had normal glucose toler-ance as determined by the National Diabetes Data Group guidelines. Each individual completed two hyperinsulinemic euglycemic clamps at insulin infusion rates of 15 (LO) and 40 (HI) mU=m-Z=min-l, one-18 h after a training bout and the second after 6 days of inactivity (IA). Muscle biopsies for the measurement of GLUT-4 were obtained from the gastrocne-mius before each clamp. Glucose disposal rates during the last 30 min of each insulin infusion were significantly reduce