Journal of Applied Physiology, Vol 81, Issue 3 1162-1168, Copyright © 1996 by American Physiological Society

ARTICLES

Effect of reduced training and training cessation on insulin action and muscle GLUT-4

J. A. Houmard, G. L. Tyndall, J. B. Midyette, M. S. Hickey, P. L. Dolan, K. E. Gavigan, M. L. Weidner and G. L. Dohm
Human Performance Laboratory, East Carolina University, Greenville, North Carolina 27585, USA.

This study examined the impact of a 50% reduction in training frequency or training cessation on insulin action and muscle GLUT-4 protein concentration. Middle-aged individuals were tested before and after 12 wk of exercise training (4 days/wk, 40-45 min/day). Subjects then either maintained training (n = 9), reduced training frequency by 50% (n = 11), or stopped exercising (n = 10) for the ensuing 2 wk. GLUT-4 protein concentration and insulin action (insulin sensitivity index, as determined by the minimal model) increased (P < or = 0.05) by an average of 1.6- and 1.9-fold, respectively, with the 12 wk of training. Insulin action and GLUT-4 did not increase further with the additional 2 wk of training in the maintained training group. Similarly, insulin sensitivity index and GLUT-4 concentration remained at trained levels when training frequency was reduced by 50% for 2 wk. GLUT-4 concentration and insulin action, however, were not different from sedentary values after 14 days of training cessation. These findings indicate that a 14-day 50% reduction in exercise frequency maintains the improvements in GLUT-4 protein concentration and insulin action gained with endurance training in moderately trained middle-aged adults; in contrast, these adaptations are largely lost with training cessation.

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