Involvement of Resting Heart Rate Variability in Chronotropic Responses During Exercise

Abstract

PURPOSE:Although resting heart rate variability (HRV) and chronotropic responses (CR) are common prognostic factor for cardiovascular disease, it is still unknown whether relationships between two variables are affected by exercise. The current study was aimed to identify correlations between resting cardiac autonomic regulation and graded exercise test-derived CR.METHODS:We recruited apparently healthy men college students aged between 20 and 29 years (n=46). They were assigned to Lowand High groups which have been determined for medians involved in resting heart rate (HR) or HRV indices such as rMSSD, HF, and LF/HF ratio, respectively. CR and post-exercise heart rate recovery (HRR) were calculated from HR fluctuations during and after symptom-limited graded exercise test using the Bruce protocol.RESULTS: In HRR, there were no significant differences between all Low and High groups separated by resting levels of HR or HRV indices. However, all Low groups assigned according to resting cardiac vagal-related HRV indices such as rMSSD and HF showed significantly lower CR levels than those of High groups, respectively. Moreover, CRs derived from stage 1-3 of Bruce protocol were positively correlated resting rMSSD and HF levels, respectively.CONCLUSIONS:The findings of the current study suggest that resting levels of cardiac vagal-related HRV indices may have an impact on CR derived from a graded exercise test, as well as there is a significant association between resting cardiac vagal activity and HR response during incremental exercise.