Effects of combined training on heart rate variability and cardiac function and structure in individuals with grade 1 obesity

Excess body fat, particularly in the abdominal region, increases the risk of cardiovascular disease. Conversely, aerobic training can induce beneficial effects on heart rate variability (HRV), as well as on cardiac structure and function, along with favorable changes in body composition. However, the interrelationship between changes in HRV, cardiac parameters, and adiposity induced by combined training (strength training followed by aerobic training; CT) in obese individuals remains unclear. Therefore, the present study evaluated the effects of 24 weeks of CT on body composition, physical fitness, ultrasonography-based abdominal fat estimation, echocardiographic parameters, and HRV in obese individuals without dietary modifications. Twenty-eight obese middle-aged men participated in the study: 16 individuals were part of the combined training group (CTG), performing resistance and aerobic training three times per week (~60 min per session), and 12 individuals comprised the control group (CG), who did not engage in any structured training program. Following the intervention, improvements were observed in echocardiographic functional variables, including systolic myocardial velocity, early diastolic myocardial velocity, the ratio of early to late diastolic myocardial velocity, peak early diastolic filling velocity, and the ratio of peak early to late diastolic filling. Additionally, significant enhancements in HRV parameters (RR interval, RMSSD, and low- and high-frequency components) were detected. Concomitantly, reductions in visceral adiposity were documented. Furthermore, significant correlations were observed between adaptations on cardiac functional and HRV indices with clinical variables. Collectively, these findings suggest that CT promotes favorable cardiac functional adaptations that are closely associated with enhanced HRV, while simultaneously reducing visceral adiposity and improving clinical variables.