Cardiac hypertrophy in athletes.

The outstanding physical ability of top athletes and the frequency with which world records are broken continue to fascinate layman and physiologist alike. It is generally assumed that such great achievements are the outcome of ever more rigorous and prolonged training programmes, which cause, among other things, adaptation of the heart in various ways. The most prominent of these is left ventricular hypertrophy. It is appropriate that in this Olympic year the significance of this hypertrophy should be discussed. Different sports require different types of muscular effort. Endurance sports, such as running, involve mainly dynamic or isotonic effort. These sportsmen seldom appear as muscular as weight lifters, wrestlers, and throwers, in whom resistive or isometric exercise is important. Cyclists perform dynamic exercise with the legs and resistive exercise with the arms. In disease states there are different responses of the left ventricle to pressure and volume overload, and, by analogy with these, workers have sought differences in the cardiac hypertrophy between resistive and endurance athletes. The results have not been consistent. Some claim to have shown that endurance athletes undergo cardiac dilatation and hypertrophy, thus preserving the ratio of left ventricular wall thickness to cavity radius within the normal range. In "resistive" athletes the wall thickness was disproportionately large. ' One group go so far as to liken the first group to congestive cardiomyopathy and the latter to hypertrophic cardiomyopathy (although the implication that the hypertrophy could be pathological is not justified).2 Other workers have failed to show these differences. As with many controversial subjects, there are now numerous published reports, and two more papers contributing to the debate are published in this issue of the British Heart Joumal. At first sight their