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 versus 73.40 +/- 40.70 ms, p < 0.05, RMSSD; 54.45 +/- 56.04 versus 81.26 +/- 60.14 ms, p < 0.05). HRrest decreased significantly following training (73.94 +/- 13.2 versus 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.

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