The effect of whole-body high-intensity interval training on heart rate variability in insufficiently active adults

Background/objective: Low physical activity is a risk factor for cardiovascular disease (CVD) and all-cause morbidity and mortality. CVD alters heart rate variability (HRV). Interestingly, HRV can improve after exercise training. Therefore, this study aimed to examine the effect of whole-body high-intensity interval training (whole-body HIIT) on HRV in low physical activity adults. Methods: Twenty-one low physical activity young adults were randomly assigned into two groups: whole-body HIIT (n = 10, females = 2/males = 8, age 22 +/- 0.8 years, BMI 19.5 +/- 1.0 kg/m2) and control (n = 11, females = 4/males = 7, age 21.7 +/- 0.8 years, BMI 19.8 +/- 0.9 kg/m2). A 6-week exercise program (3 days per week) consisting of 10 min of whole-body HIIT (burpees, mountain climbers, jumping jacks, and squats) at their maximal effort was administered. Baseline and post-training HRV (time domain: SDNN and RMSSD, frequency domain: LF, HF, and LF/HF ratio) and resting heart rate (HRrest) were recorded. Results: The time domain parameter increased significantly in the whole-body HIIT group (SDNN; 50.95 +/- 37.17 vs. 73.40 +/- 40.70 ms, p < 0.05, RMSSD; 54.45 +/- 56.04 vs. 81.26 +/- 60.14 ms, p < 0.05). HRrest decreased significantly following training (73.94 +/- 13.2 vs. 66.1 +/- 10.8 bpm, p < 0.05). However, there were no significant differences in all frequency-domain parameters. Conclusion: Six weeks of whole-body HIIT improved cardiovascular autonomic function in insufficiently active adults. Thus, whole-body HIIT might be considered an alternative exercise for reducing the risk of CVD. (C) 2021 The Society of Chinese Scholars on Exercise Physiology and Fitness. Published by Elsevier (Singapore) Pte Ltd.