The purpose of this study was to compare stroke volume (SV) and myocardial contractility responses during and immediately after upper- and lower-body exercise. Nine men (mean 28 yr, 78 kg) completed progressive intensity discontinuous tests on both an arm crank and cycle ergometer. Exercise for each power output (PO) was 7 min with 20-min rest periods interspersed. Impedance cardiography was used to measure cardiac output (Q), SV, and contractility on a beat-by-beat basis during exercise and a 15-s recovery period. Q increased linearly, and total peripheral resistance decreased exponentially with increasing PO levels. During recovery from exercise, the Q and heart rate (HR) values decreased immediately at all PO levels. When the exercise VO2 exceeded 1.0 1 X min-1, SV fell significantly during recovery for both exercise modes. In general, the recovery myocardial contractility indices remained similar to exercise values. It was concluded that immediately after low intensities of exercise, Q decreases because of a fall in HR. After moderate- and high-intensity exercise, Q decreases because of a fall in both HR and SV.
Myocardial contractility indices based on strain imaging
