Central and peripheral hemodynamics during maximal leg extension exercise

Summary

The purpose of this study was to examine the central and peripheral hemodynamic adaptations to maximal leg extension exercise. Seventeen men (¯X=25 years, 84 kg) performed leg extension exercise (Universal equipment) for 12 repetitions (90s) to fatigue. Each repetition consisted of a 3s lifting motion, 1s pause, and 3s lowering motion. Impedance cardiography was used to measure stroke volume (SV), cardiac output ($\dot V_{{\text{O}}_{{\text{2 max}}} }$), systolic time intervals, and impedance contractility indices on a beat-by-beat basis. There were significant increases in systolic, diastolic, mean arterial pressure, total peripheral resistance, and HR during exercise. The mean$\dot Q$ remained similar throughout the protocol. SV decreased even though indices of myocardial performance indicated an enhancement of contractility. The magnitude of$\dot Q$ and SV were dependent upon the phase of leg extension. SV and$\dot Q$ during the lifting portions of the exercise were smaller than the lowering portions. The differences in SV and$\dot Q$ during the concentric and eccentric phases of the exercise most likely reflect the large static forces in exercising muscle which impeded venous return and increased afterload.