CARDIOVASCULAR ADAPTATIONS TO 10 DAYS OF CYCLE EXERCISE

We hypothesized that 10 days of training would enhance cardiac output (GO) and stroke volume (SV) during peak exercise and increase the inot ropic response to P-adrenergic stimulation. Ten subjects [age 26 +/- 2 (SE) yr] trained on, a cycle ergometer for 10 days. At peak exercise, training increased Oz uptake, CO, and SV (P < 0.001). Left ventricula r (LV) size and function at rest were assessed with two-dimensional ec hocardiography before (baseline) and after atropine injection (1.0 mg) and during four graded doses of dobutamine. LV end-diastolic diameter increased with training (P < 0.02), whereas LV wall thickness was unc hanged. LV contractile performance was assessed by relating fractional shortening (FS) to the estimated end-systolic wall stress (rho(ES)) T raining increased the slope of the FS-sigma(ES) relationship (P < 0.05 ), indicating enhanced systolic function. The increase in slope correl ated with increases in CO (r = -0.71, P < 0.05) and SV (r = -0.70, P < 0.05). The increase in blood volume also correlated with increases in CO (r = 0.80, P < 0.01) and SV (r = 0.85, P < 0.004). These data show that 10 days of training enhance the inotropic response to P-adrenerg ic stimulation, associated with increases in CO and SV during peak exe rcise.