Effect of exercise on cardiac muscle performance in aged rats.
Most investigations of a direct impact of chronic physical conditioning on cardiac muscle physiology and biochemistry have utilized relatively young animal models. Some, but not all, of these studies have demonstrated beneficial effect of relatively modest magnitude. With advancing age, i.e., with the onset of senescence, characteristic changes in many aspects of cardiac physiology and biochemistry in rodent models have been noted to occur. In general, these consist of a reduction in the kinetics of events that determine myocardial excitation-contraction relaxation and energetics. Recently it has been shown that several of these apparent age-related functional declines can be reversed by chronic physical conditioning, which in some instances have no effect on cardiac muscle of younger animals. This suggests that the relative efficacy of chronic exercise to modulate myocardial performance may, in part, be determined by the level of function present before the intervention, as is the case for other modulators of cardiac muscle function. In addition, that apparent age-related deficits in myocardial function can be reversed by conditioning suggests an interaction between life-style and aging.