Alireza Ghardashi-Afousi - PhD Candidate, Department of Exercise Physiology, School of Physical Education and Exercise Sciences, University of Tehran AND Exercise Physiology Research Center, Life Style Institute, Baqiyatallah University of Medical Sciences, Tehran, Iran
Mohammad Taghi Holisaz - Professor, Department of Physical Medicine and Rehabilitation, School of Medicine, Baqiyatallah University of Medical Sciences, Tehran, Iran
Hossein Shirvani - Assistant Professor, Exercise Physiology Research Center, Life Style Institute, Baqiyatallah University of Medical Sciences, Tehran, Iran
Bahram Pishgoo - Associate Professor, Atherosclerosis Research Center, School of Medicine, Baqiyatallah University of Medical Sciences, Tehran, Iran

BACKGROUND: Heart rate variability (HRV) declines after coronary artery bypass grafting (CABG). The purpose of this study was to evaluate the effect of low-volume high-intensity interval training (LV-HIIT) and moderate-intensity continuous training (MICT) on HRV as well as, hemodynamic and echocardiography indices.METHODS: Forty-two men after CABG (۵۵.۱۲ ± ۳.۹۷ years) were randomly assigned into LV-HIIT, MICT, and control (CTL) groups. The exercise training in LV-HIIT consisted of ۲-minute interval at ۸۵-۹۵ percent of maximal heart rate (HRmax), ۲-minute interval at ۵۰% of HRmax and ۴۰-minute interval at ۷۰% of HRmax in MICT for three sessions in a week, for ۶-weeks. HRV parameters were evaluated by ۲۴-hour Holter electrocardiography (ECG) recording, and echocardiography parameters at baseline and end of intervention were measured in all ۳ groups.RESULTS: At the end of the intervention, left ventricular ejection fraction (LVEF) significantly increased in LV-HIIT group (۵۸.۵۳ ± ۷.۲۶ percent) compared with MICT (۵۲.۲۶ ± ۷.۹۱ percent) and CTL (۴۹.۶۸ ± ۷.۲۷ percent) groups (P < ۰.۰۰۱). Furthermore, mean R-R interval, root mean square successive difference (RMSSD) of R-R interval, and standard deviation of R-R interval (SDRR) in LV-HIIT group considerably increased compared with MICT group (P < ۰.۰۰۱). High-frequency power (HF) significantly increased in LV-HIIT and MICT groups compared with CTL group (P < ۰.۰۰۱). On the other hand, low frequency (LF) and LF/HF ratio significantly decreased in LV-HIIT group in comparison with MICT group (P < ۰.۰۱۰).CONCLUSION: These results suggest that LV-HIIT has a greater effect on improvement of cardiac autonomic activities by increasing R-R interval, SDRR, RMSSD, and HF, and decreasing LF and LF/HF ratio in patients after CABG.

High-Intensity Interval Trainin, Continuous Training, Cardiac Rehabilitation, Cardiac Autonomic Activity