Effect of short- and long-term endurance training on creatine phosphokinase activity in skeletal and cardiac muscles of CW-1 and C57BL mice.

Creatine phosphokinase (CPK) has been shown to provide the initial ATP for muscle contraction. The effect of wheel running on CPK levels was compared in hindleg and cardiac muscles of young, intermediate-age and old outbred CW-1 and inbred C57BL mice. Short-term (5 weeks) and long-term (over 12 months) regimens were used in these studies. It was shown that as a function of age there was a 20-30% decrease of CPK activity in hindleg muscles of old sedentary animals. No change with age was observed in cardiac muscles of old animals. Short-term exercise of 5 weeks resulted in an increase in CPK levels in young running mice in both hindleg and cardiac muscles. In old animals there was a slight decrease in striated hindleg muscles, but no change in cardiac muscles. In the long-term exercise group, young (6-month-old) and intermediate-age (15-month-old) animals showed a 20-40% increase in CPK specific activity in hindleg muscles over sedentary control mice. No such increase in CPK activity was observed in old trained mice. However, the long-term exercise regimen prevented the age-associated decline in CPK activity found in sedentary animals.