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

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 beta-blockade. We also sought to determine whether men and women had a similar cardiac reserve capacity for increasing stroke volume with beta-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 beta-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, beta-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 beta-blockade was significantly less while cardiac output was reduced more. There were no gender differences in the effects of beta-blockade on HR, stroke volume, or cardiac output. These data indicate that, during exercise with beta-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.