Journal of Applied Physiology, Vol 57, Issue 6 1834-1841, Copyright © 1984 by American Physiological Society
Reduced training frequency effects on aerobic power and muscle adaptations in rats
R. C. Hickson, S. M. Overland and K. A. Dougherty
Female rats were exercised by swimming up to 4 h/day either 2, 4, or 6
days/wk. After 7 wk they continued to train at these frequencies or had
their training reduced from 6 to 4, 2, or 0 days/wk for an additional 9 wk.
Ventricular weights and maximum O2 uptake (VO2max) were increased by 5-10%
after training 2 days/wk, 15-17% after 4 days/wk, and 25-30% after 6
days/wk. Following reduced training, VO2max was similar when the 4- or
2-day/wk reduced training groups are compared with their 4- or 2-day/wk
continued training counterparts. In contrast, VO2max was greater in the
0-day reduced than in the sedentary control group. No differences in
mitochondrial markers or myoglobin content in red or mixed skeletal muscles
were found between training 2 or 4 days/wk vs. reduced training at
comparable frequencies. O2 uptake capacity of plantaris muscles and
myoglobin concentration in fast-twitch red vastus lateralis muscles were
greater in the 0-day reduced group than in the sedentary controls. These
data show that VO2max and certain markers of aerobic metabolism in skeletal
muscles of rats are lost at a slower rate than their rate of increase from
the untrained state. However, a reduction of swimming frequency from 6 to 4
or 2 days/wk is not a sufficient stimulus to maintain VO2max, cardiac
enlargement, or the increased aerobic potential of skeletal muscle at the
6-day/wk levels.(ABSTRACT TRUNCATED AT 250 WORDS)
