Effect of Supine Exercise

RESPONSE to physical exercise in man has been studied extensively. For any given workload, a predictable change in blood pressure, heart rate, and cardiac output has been shown to occur. Rushmerl has pointed out that the response of stroke volume to exercise, however, may be variable both in experimental animals and in man. He has also demonstrated that not only the amount, but also the direction of change in cardiac dimensions may vary in the exercising dog, thus indicating that the pattern of response cannot be readily predicted. In a preliminary report using radiocardiography, Cournand and associates2 demonstrated that the heart emptied more completely during physical exercise. In a recent study measuring cardiac dimensions by means of silver clips sewn on the heart of four postoperative subjects, Braunwald and associates3 showed that these dimensions diminished on the average of 3 to 5 per cent during supine leg exercise. It is the purpose of this report to present data obtained in 20 human subjects with minimal heart disease on the change induced by supine leg exercise in left ventricular volume, in the degree and speed of ventricular emptying, and to describe the relationship of this mechanical activity to myocardial oxygen consumption.