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

Figures

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  Figure 1. Distribution of cardiorespiratory fitness indicators across physical activity groups. Box plots illustrate the distributions of functional capacity, absolute VO2max (L·min−1), relative VO2max (mL·kg−1·min−1), and vital capacity (L) among participants with low (n = 87), medium (n = 76), and high (n = 21) physical activity levels. Group differences were assessed using the Kruskal-Wallis test, followed by Dunn’s post hoc tests with Holm correction for pairwise comparisons. Outliers are shown as individual points. Significance levels: *P < 0.05; **P < 0.01; ***P < 0.001; NS, not significant (P ≥ 0.05).

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  Figure 2. Distribution of log-transformed HRV indices across physical activity groups. Box plots present log-transformed time-domain indices (Mean-RR interval, SDNN, RMSSD) and frequency-domain indices (LFn, HFn, and LF/HF ratio) for participants classified into low (n = 87), medium (n = 76), and high (n = 21) physical activity levels. Overall group differences were analyzed using the Kruskal-Wallis test, followed by Dunn’s post hoc tests with Holm correction. Outliers are shown as individual points. Significance levels: *P < 0.05; **P < 0.01; NS = P ≥ 0.05.

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  Figure 3. Heatmap of correlations among physical activity, cardiorespiratory fitness, body composition, and HRV indices. Heatmap illustrating the correlations among physical activity (PA), cardiorespiratory fitness variables (functional capacity, vital capacity, and VO2max), body composition indices (BMI, SLM, BFP%, VFC, and WHR), and heart rate variability (HRV) indices (MeanRR, SDNN, RMSSD, LFn, HFn, and LF/HF). The color scale indicates the direction and magnitude of the correlations, with blue denoting positive and brown denoting negative associations. Non-significant correlations (P ≥ 0.05) are marked with “×”.

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  Figure 4. Forest plot of multivariable regression analysis for HRV indices. Forest plot illustrating the results of stepwise multiple regression analyses examining the associations of HRV indices with physical activity, BFP%, and sex. All HRV variables were log-transformed prior to modeling. Relative maximal oxygen uptake (VO2max) was also log-transformed and is denoted as log VO2max_rel. Regression coefficients are shown with 95% confidence intervals. A P-value < 0.05 was considered statistically significant.