Changes in stroke volume with β-blockade before and after 10 days of exercise training in men and women

Mier, Constance M., Melissa A. Domenick, and Jack H. Wilmore. Changes in stroke volume with β-blockade before and after 10 days of exercise training in men and women. J. Appl. Physiol. 83(5): 1660–1665, 1997. We sought to determine whether 10 days of training would be a sufficient stimulus for cardiac adaptations that would allow a greater compensatory stroke volume during β-blockade. We also sought to determine whether men and women had a similar cardiac reserve capacity for increasing stroke volume with β-blockade during submaximal exercise. Eight men (age 29 ± 2 yr, mean ± SE) and eight women (25 ± 2 yr) cycled at 65% of peak O2 consumption (unblocked) under placebo-control and β-blockade (100 mg atenolol) conditions performed on separate days. These tests were repeated at the same power output after training (10 consecutive days, 1 h of cycling per day). Before training, β-blockade significantly ( P < 0.05) decreased heart rate (HR) and cardiac output and increased stroke volume in both men and women. After training, the increase in stroke volume and decrease in HR with β-blockade was significantly less while cardiac output was reduced more. There were no gender differences in the effects of β-blockade on HR, stroke volume, or cardiac output. These data indicate that, during exercise with β-blockade, exercise training for 10 days does not enhance the compensatory increase in stroke volume and that men and women have a similar cardiac reserve capacity for increasing stroke volume.