[Influence of long-term swimming training on the structure and enzyme activity of myosin in the rat myocardium (author's transl)].

Intermittent hemodynamic loading of the rat myocardium due to swimming training for several weeks leads to a significant increase in the specific ATPase activity of myosin. This enzymatic alteration of the myosin molecule is accompanied by changes in the stoichiometry of its light chains which are of great significance for the ATPase activity. The maximum shortening velocity of the unloaded myocardium (Vmax), estimated on the basis of afterloaded contractions, shows a slight increase as a result of the physical training. Since, on the other hand, the increase is not significant using the quick release technique, a close relationship between the specific ATPase activity and the augmented cross-sectional contractile capability cannot be proved in our experiments.