Central Circulatory Adaptations to Physical Training

The bradycardia effect of a 10-week jogging program was studied in 13 previously sedentary middle-aged subjects (seven women and six men). This response during standardized submaximal treadmill walking and leg cycling was related to changes in cardiac output ([Qdot]), stroke volume (SV), and arteriovenous oxygen differences (a-vO2 diff). Heart rate (HR) response was also studied during load carrying and arm cycling tasks, and a [Vdot]O2 max test was administered. All tests were repeated posttraining. The posttraining increases in [Vdot]O2 max (ml/kg × min-1) were 19.7% and 14.8% for the men and women respectively. Training also produced significant reductions in submaximal HR and Q during treadmill and leg cycling exercise. A-vO2 diff rose, while there were no changes in [Vdot]O2 during the submaximal work tasks, suggesting either altered blood flow or a greater capacity to utilize O2 by the working muscle. Both men and women showed significant reductions in HR during the arm cycling and load carrying as well. These data suggest that a jogging program can alter cardiovascular function in tasks other than running. The magnitude and direction of change showed no sex differences; therefore, it was also concluded that there are no differences in the trainability of previously sedentary middle-aged men and women.