Endurance training fails to correct age‐related declines in cardiovagal control

Abstract

This study tested the hypothesis that long‐term endurance training (ET) preserves cardiovagal control in aging individuals. Baroreflex sensitivity (BRS) and the rapid heart rate response at exercise onset (ΔHR) reflect levels of cardiovagal control. BRS declines with age and cardiovascular disease but, reportedly, this effect can be reversed by ET. It remains unclear if ET also preserves ΔHR (reflecting removal of parasympathetic cardiac inhibition). Both BRS (sequence method, 5–10 min of baseline) and ΔHR to three, 30s contractions at 40% of their maximum voluntary contraction strength, were assessed in a group of young individuals (Y; age=26±4) and in groups of older individuals who were healthy (O; age=56±4), endurance trained (ET; age=55±4) or entering cardiac rehabilitation (CR; age=59±4) (n=15 for each group). Compared with Y (10±9 bpm), ΔHR was less in CR (3±2 bpm; P<0.05) but not the other groups (O: 7±5, ET: 5±3 bpm; NS). Similarly, compared with Y (30±15 ms/mmHg), BRS was less in CR (14±12 ms/mmHg) but not the other groups (O: 20±12, ET: 25±15 ms/mmHg). Contrary to previous results, ET did not preserve BRS at levels expressed in Y. However, age correlated strongly with BRS and ΔHR (r=−0.4, p=0.001; r=−0.3, p=0.013 respectively) across all groups. The results suggest that age exerts a dominant impact on cardiovagal control and that this effect remains difficult to restore with long‐term ET. Supported by CIHR.