Abstract

The purpose of the study was to investigate the circulorespiratory (CR) response of a group of 9 untrained men to treadmill (T) and bicycle (B) exercise during a 60-minute exercise period (XT). Following the determination of mode specific age-adjusted maximum oxygen uptake (V02 max) utilizing T and B ergometers, 2 separate XT were administered at 50 of the V02 max utilizing T and B ergometers. During XT cardiac output (C02 rebreathing), oxygen consumption, rectal temperature and blood pressure were monitored at 15-minute intervals. Data were analyzed by use of multiple linear regression analysis to determine (1) the mode dependent variability in the CR response to prolonged aerobic activity and (2) the effect of extending the duration of exercise. A significant mode dependent variance in the CR response to exercise at the sameenergy expenditure was seen. During the TXT, mean cardiac output was 6.3 greater than during the BXT while the calculated stroke volume was 13.4 greater during the TXT. The rate pressure product (RPP) was 9.4 greater during the BXT and inferred greater myocardial oxygen consumption during pedaling activity even though the cardiac output was less during the BXT. There were no significant differences betweenthe modes of exercise in the regression equations of heart rate, cardiac output or blood pressure over time. Verf.-Referat