Effect of endurance exercise training on muscle glycogen
supercompensation in rats.
Nakatani, Akira, Dong-Ho Han, Polly A. Hansen, Lori A. Nolte, Helen H.
Host, Robert C. Hickner, and John O. Holloszy.
Department of Internal Medicine, Washington University School of
Medicine, St. Louis, MO 63110
APStracts 3:0532A, 1996.
The purpose of this study was to test the hypothesis that the rate and
extent of glycogen supercompensation in skeletal muscle are increased
by endurance exercise training. Rats were trained using a 5wk-long
swimming program in which the duration of swimming was gradually
increased to 6h/day over 3 weeks and then maintained at 6h/day for an
additional 2 wk. Glycogen repletion was measured in trained and
untrained rats after a glycogen depleting bout of exercise. The rats
were given a rodent chow diet plus 5% sucrose in their drinking water
ad libitum during the recovery period. There were remarkable
differences in both the rates of glycogen accumulation and the
glycogen concentrations attained in the two groups. The concentration
of glycogen in epitrochlearis muscle averaged 13.1 +/- 0.9 mg/g wet
wt in the untrained group and 31.7 +/- 2.7 mg/g in the trained group
(p<0.001) 24h after the exercise. This difference could not be
explained by a training effect on glycogen synthase. The training
induced 50% increases in muscle GLUT4 glucose transporter protein and
in hexokinase activity in epitrochlearis muscles. We conclude that
endurance exercise training results in increases in both the rate and
magnitude of muscle glycogen supercompensation in rats.
Received 1 October 1996; accepted in final form 18 November 1996.
APS Manuscript Number A943-6.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996