Energetics of myocardial function.

ABSTRACT

The question of whether the heart in humans is resistant to deterioration during prolonged exercise is addressed in this review. An evaluation of the available data in the literature shows 1) whole body VO2 increases during vigorous prolonged exercise, primarily due to an increase in O2 consumption of working muscles; 2) heat exacerbates the rise in VO2; 3) these factors, hard exercise and heat, induce cardiovascular drift which involves progressive decreases in mean arterial pressure and stroke volume, with heart rate increasing to maintain cardiac output; 4) the fall in stroke volume appears to occur, at least in part, because ventricular filling pressure is lowered with a fall in central venous volume as cutaneous venous volume increases; 5) there is some limited indirect evidence that the inotropic state of the heart may also decrease with prolonged exhaustive exercise; and (6) neither estimates of heart work nor myocardial energetics appear to change in healthy men after 1 h of exercise under temperate conditions.