Effect of reduced training and training cessation on insulin action
and muscle glut-4.
Houmard, Joseph A., Gilian L. Tyndall, Jack B. Midyette, Matthew S.
Hickey, Patricia L. Dolan, Karen E. Gavigan, Melinda L. Weidner, and
G. Lynis Dohm.
Human Performance Laboratory and Department of Biochemistry, East
Carolina University, Greenville, NC 27585 USA
APStracts 3:0186A, 1996.
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 weeks of exercise training (4 days/week, 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 weeks. GLUT-4 protein concentration and insulin action (SI, as
determined by the minimal model) increased (P<0.05) by an
average of 1.6 and 1.9 fold, respectively, with the 12 weeks of
training. Insulin action and GLUT-4 did not increase further with the
additional 2 weeks of training in the maintained training group.
Similarly, SI and GLUT-4 concentration remained at trained levels
when training frequency was reduced by 50% for 2 weeks. 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.
Received 26 January 1996; accepted in final form 27 March 1996.
APS Manuscript Number A89-6.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 16 April 96