Effects of voluntary physical exercise on cardiac function and energetics in spontaneously hypertensive rats.

The influence of voluntary physical exercise in running wheels on myocardial function, cardiac oxygen utilization and cardiovascular response to emotional stress was analysed in the spontaneously hypertensive rat. After 6 weeks of exercise, a significant increase in resting cardiac output was found, which was due to an elevation of stroke volume. However, voluntary training for 12 weeks had no effect on resting blood pressure or on the blood-pressure response to mental stress. Cardiac function was also examined in vitro. At a low aortic diastolic pressure, it was markedly augmented in trained spontaneously hypertensive rats. At high aortic diastolic pressure, maximal cardiac function was similar in the two groups. Myocardial oxygen consumption (mumol min-1 g-1) for a given level of external work was reduced in trained, compared with non-exercised control spontaneously hypertensive rats. Chronic physical exercise thus greatly improved myocardial function at a subnormal perfusion pressure, suggesting better nutritional supply to the myocardium, probably created by an increased capillary surface area.