Heart volume during prolonged exercise in the supine and sitting position.

Abstract

AbstractThe roentgenological heart volume was studied in 10 healthy young men during prolonged continuous exercise of constant intensity in the sitting position and in 6 subjects also in the supinr position. The work load was on an average 760.0 kpm/min in the sitting and 758.3 kpm/min in the supine position. The heart rate in the sitting position after 3–9 min exercise was 139.5 beats/min and 171.0 beats/min at the end of work, mean work time 56.5 min. The corresponding figures in the supine position were 127.8 and 156.7 beats/min, with a mean work time of 64.0 min. The exposure of the roentgen film was made in end‐diastole. During the continuous exercise at a constant load there was a continuous fall of the heart volume in both body positions accompanied by a continuous increase in heart rate. There Lvas a significant regression of total heart volume on heart rate. The rate of change in heart volume was 37.5 ml and 58.3 ml per 10 beats/min change in heart rate in the sitting and supine positions respectively. The maximum decrease was on an average 81.1 ml and 110.5 ml with an increase in heart rate of 28.6 beats/min and 24.8 beats/min in the sitting and supine position respectively. Close to exhaustion, the heart volume increased in 6 of 10 subjects in the sitting position by, on an average, 52.5 ml (probably significant) and in 3 of 6 in supine by. on an average, 42.0 ml in spite of a further increase in heart rate.