The impact of physical activity levels and cardiorespiratory fitness on heart rate variability in overweight and obese college students: a cross-sectional study

Objective This study aimed to examine the impact of varying physical activity (PA) intensities on heart rate variability (HRV), to explore the relationships among cardiorespiratory fitness (CRF), body composition, and HRV, and to further characterize sex-specific HRV patterns in overweight and obese college students. Methods A total of 184 overweight or obese college students were enrolled in this cross-sectional study. Participants were categorized into low, medium, or high intensity PA groups using the International Physical Activity Questionnaire–Short Form (IPAQ-SF). Body fat percentage and muscle mass were assessed using bioelectrical impedance analysis, while CRF was estimated from maximal oxygen uptake (VO 2 max) derived from a cycle ergometer test. Resting HRV indices were obtained under standardized conditions. Differences in body composition, CRF, and HRV were analyzed across groups. Multiple linear regression models were further employed to identify independent predictors of HRV. Results High-intensity PA independently predicted log(standard deviation of normal RR intervals (SDNN)) (b = 0.40, 95% CI [0.12–0.67], P = 0.005) and log(root mean square of successive differences (RMSSD)) (b = 0.48, 95% confidence interval (CI) [0.13–0.83], P = 0.007), while medium-intensity PA also showed a significant effect on log(SDNN) (b = 0.22, 95% CI [0.04–0.39], P = 0.014). Female participants exhibited higher log(high-frequency component (HFn)) (b = 0.25, 95% CI [0.11–0.39], P < 0.001) and lower log(low frequency/high frequency (LF/HF)) (b = −0.39, 95% CI [−0.62 to −0.17], P < 0.001) compared with males. VO 2 max was not significantly associated with most HRV indices, remaining significant only for log(SDNN) (b = 0.46, 95% CI [0.02–0.90], P = 0.042). Conclusions Medium-to-high intensity PA independently predicted favorable HRV indices. Female students demonstrated higher HRV levels than males, suggesting sex specific. The association between PA and autonomic regulation appeared stronger than that between VO 2 max and HRV.