Effects of Different Exercise Modalities on Heart Rate Variability in Community-Dwelling Adults With High Visceral Adipose Tissue: A Randomized Crossover Trial

Background: – Heart rate variability (HRV) is often reduced in individuals with high visceral adipose tissue (VAT), a major cardiovascular risk factor. Both high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) can improve HRV and reduce VAT, but the optimal approach remains unclear. Objective: – Our aim is to compare the effects of 8 weeks of HIIT and MICT on HRV, with body composition as a secondary outcome. Methods: – A two-stage randomized crossover trial was employed to include 31 community-dwelling adults aged 40 to 64 years with high VAT (≥100 cm²). The participants were randomly allocated to either HIIT (n = 16) or MICT (n = 15) groups; the intervention lasted 8 weeks. This was followed by an 8-week washout period (no exercise). Subsequently, they crossed over to the alternate modality and trained for 8 weeks. Heart rate variability and body composition were assessed both before and after each stage. Generalized estimating equations were used to compare outcomes between the 2 groups. Results: – The HIIT group exhibited a significantly lower low frequency/high frequency ratio than did the MICT group; therefore, HIIT outperformed MICT in improving autonomic balance (B = 0.77; P =.039). No significant between-group difference was observed in body composition changes. Both HRV and body composition improved during the exercise stages but declined during the washout period. Conclusions: – Eight weeks of HIIT, 3 times a week, was more effective than MICT in improving cardiac autonomic function in adults with high VAT. Health professionals should encourage sustained structured physical activity to maintain HRV benefits.