Effects of exercise on the biochemical aging of mammalian myocardium. II. Creatine phosphokinase.

Male Fischer 344 rats from a long inbred colony (by brother-sister mating) were subjected to moderate (forced swimming) physical activity on a regular basis, beginning at 3 weeks following weaning. Normally caged, sedentary littermates were employed as controls at each age level. Exercised animals showed a greater total ventricular mass and correspondingly lower body weight, and the heart to body weight ratio for experimental animals about 25% higher at all ages, beginning at 3 months following onset of exercise. Finally, the specific activity of myocardial creatine phosphokinase was consistently higher for the exercised animals, beginning at 3 months of age and through 16 months of such exercise. These data support previous findings from this laboratory, as well as by others, that long-term moderate exercise begun early in life has a continuing, beneficial effect on the mammalian heart, both at the gross functional and intracellular biochemical levels.