Post-aerobic-exercise autonomic responses in hypertensives — a randomized controlled trial

Background. Heart rate variability (HRV) response to an exercise bout may provide useful insight into autonomic stress reactivity. Considering that cardiovascular responses to a stressor may be predictive of certain diseases, it becomes critical to understand if high blood pressure can influence the autonomic nervous system response to acute exercise. We, therefore, undertook a study to investigate the effect of a single bout of aerobic exercise on autonomic responses in hypertensives. Material and methods. Twenty hypertensives were randomly assigned to one of the two experimental groups [control (CG) or exercise (EG)]. The exercise session was conducted on a treadmill and consisted of 40 min of running/walking at 60–70% HRreserve. In the control session, the participants remained seated in a quiet room for 40 min. After the exercise/control sessions, the HRV was recorded continuously for 60 min. Results. The EG presented an increase with a large effect size for LF [1.0 (post-30) and 1.0 (post-60)] and LF/HF [0.8 (post-30) and 1.1 (post-60)]. Additionally, a reduction with a large effect was observed for HF [–1.0 (post-30) and –1.0 (post-60)]. Conclusion. There is a considerable reduction in post-aerobic-exercise parasympathetic activity and an increase in sympathetic activity. Therefore, a single bout of aerobic exercise is not able to quickly improve the cardiac autonomic regulation.