Investigating the Acute Effect of Different Training Protocols on Heart Rate Variability

Purpose: This study examined the acute effects of High-Intensity Interval Training (HIIT) and prolonged endurance training (ET) on heart rate variability (HRV) in elite Greco-Roman wrestlers. A secondary aim was to assess the usefulness of HRV in opti-mizing recovery strategies by monitoring post-exercise changes. Methods: Using a longitudinal crossover design, 13 elite male wrestlers completed two training protocols separated by a 15-day washout period. HRV variables were recorded at baseline, pre-exercise, during training, and 24 hours post-exercise. Data were analyzed with a linear mixed model (LMM) and Bonferroni-adjusted post hoc comparisons. Results: A significant main effect of Timepoint was found for all HRV parameters (SDNN, RMSSD, LF/HF ratio, and overall HRV), indicating marked reductions during exercise fol-lowed by partial recovery after 24 hours. A significant effect of Training Type was ob-served for SDNN. Post hoc analysis showed a significantly greater suppression of overall HRV during HIIT compared to ET (p = .012, Cohen’s d = 0.82). Despite these differences, both protocols demonstrated similar recovery patterns at 24 hours. Conclusion: Both HIIT and ET induced acute decreases in HRV, with HIIT causing a more pronounced decline. Nevertheless, HRV recovery after 24 hours was comparable between the two training modalities.