Cardiovagal response to acute mild exercise in young healthy subjects

Background The aim of the present study was to investigate the effect of a single bout of mild exercise on autonomic nervous system activity in healthy subjects. Methods and Results The study group comprised 18 healthy males, aged between 20 and 24 years, who had not been training regularly for the last 3 months. A supine recording of systolic arterial pressure (SAP) and RR interval and the administration of the phenylephrine test were performed at baseline and repeated after a 60-min recovery period following treadmill exercise training for 30 min at 65% of maximal heart rate. Mean SAP and RR interval, heart rate variability (HRV) indices (the standard deviation of normal-to-normal RR intervals (SDNN), the square root of the mean of squared differences between successive intervals and the percentage of adjacent RR intervals differing more than 50 ms), noninvasive spectral baroreflex sensitivity (Spe-BRS) and phenylephrine baroreflex sensitivity (Phe-BRS) were assessed before and after training. Mean SAP measured after exercise was lower than baseline (120 +/- 12mm Hg vs 128 +/- 12mm Hg, p=0.05). Spe-BRS and Phe-BRS increased significantly after exercise, from 11.8 +/- 6.1 ms/mmHg to 16.0 +/- 7.8 ms/mmHg (p=0.034), and from 16.0 +/- 8.8 ms/mmHg to 21.9 +/- 9.3 ms/mmHg (p=0.022), respectively. A parallel increase was also observed in SDNN (from 81 +/- 44 ms to 96 +/- 53 ms, p=0.02), but the other HRV indices showed no significant differences between pre- and post-exercise. Conclusions A single session of mild exercise performed by sedentary young men leads to significant autonomic nervous system improvement, which suggests that even mild physical activity is beneficial for neural cardiac regulation and should be recommended to sedentary healthy subjects.