Comparison of hemodynamic responses to static and dynamic exercise.

Eight healthy male adults (25-34 yr) were studied to compare hemodynamic responses to static exercise (30% MVC in leg extension), static-dynamic exercise (one-arm cranking, 66 and 79% VO2 max-arm), and dynamic exercise (two-leg cycling, 58 and 82% VOmax-legs). Leg extension (LE) strength was measured by a spring scale. Cranking and cycling were performed on a Quinton bicycle ergometer. VO2 was measured using an automated open-circuit system. Heart rate (HR) was monitored from a CM-5 ECG lead, and arterial pressure (Pa) was measured from an indwelling brachial artery catheter. Cardiac output (Q) was measured using a CO2-rebreathing procedure. Total peripheral resistance (TPR) was calculated using the mean arterial pressure (Pa) as the systemic pressure gradient. In 30% LE, a significant (P less than 0.05) Pa increase occurred (pressor response) mediated primarily by an increase in Q. One-arm cranking and two-leg cycling at similar relative VO2 demands resulted in nearly identical increases in Pa due to different contributions of Q and TPR. Q and the arteriovenous O2 difference varied as a function of VO2 regardless of the mode of exercise (static or dynamic). On the other hand, the HR response, which accounted for increased Q in the exercises containing a static component, and Pa varied with mode of exercise. Any generalized scheme of cardiovascular control during exercise must account for the potential influence of dynamic and static components of the exercise.