Journal of Applied Physiology, Vol 54, Issue 2 530-535, Copyright © 1983 by American Physiological Society
Effects of repetitive exercise on neonatal rat skeletal muscle oxidative capacity
A. M. MacIntosh and K. M. Baldwin
Since little is known about the training response to exercise in neonatal
animals, this study was undertaken to elucidate the potential of oxidative
system adaptations in developing skeletal muscle of rats during 50 days of
daily treadmill running. The training regimen involved male and female rats
(10 days old) initially running 0.1 mph, 0% grade, for 15 min. The program
progressed to 1 mph, 25% grade, for 60 min by 50 days of age. At 25 days of
age, pyruvate and palmitate oxidative capacity, and citrate synthase
activity in red vastus muscle homogenates were elevated in the trained
group (T) compared with age- and sex-matched controls (C). These increases
were also observed for each subsequent time point tested and occurred in
spite of the fact that the peak oxidative capacity of neonatal red vastus
muscle was 46% greater than adult values. Further, trained animals tested
at 45 days of age responded with a 12% increase in maximal oxygen
consumption (Vo2max) compared with controls (P less than 0.05). Assays of
muscle phosphofructokinase and of creatine phosphokinase activity conducted
at this time point revealed no difference between T and C groups.
Collectively, these data suggest that neonatal rats can be successfully
trained and that they respond to an endurance-type program qualitatively
similarly to adult rats.
