Influence of age and moderate-intensity exercise training on heart rate variability in young and mature adults

Abstract

The purpose of this study was to examine the influence of age on the changes in heart rate variability (HRV) following moderate intensity exercise training, and elucidate further the mechanism of training-induced bradycardia and cardioprotection. Electrocardiograms were recorded from 12 young (18-24 years) and 12 mature (29-43 years) human subjects during supine rest and submaximal moderate exercise. Recordings were obtained prior to, midway and following 16 weeks of aerobic exercise training designed to improve cardiorespiratory fitness and health. Training resulted in bradycardia during rest and all submaximal exercise workloads (p<0.05). Total HRV during rest and exercise was significantly increased for the mature subjects (p<0.05) following training while other measures of HRV were not significantly changed for either group. It was concluded that training of moderate intensity was insufficient to induce changes in the autonomic control of heart rate for young to mature subjects. The lack of HRV changes may suggest the existence of a vagal critical point, below which training induced increases in vagal activity may be forthcoming and above which, changes in vagal activity may be negligible. Training-induced bradycardia and the cardioprotective effect of regular aerobic exercise may result from factors other than an increased vagal activity.