Dynamic effects of different exercise modalities on autonomic recovery: a longitudinal study based on heart rate variability.

Purpose Post-exercise recovery is a critical window for physiological adaptation, with the autonomic nervous system (ANS) playing a key regulatory role. However, whether long-term training with different modalities systematically influences post-exercise ANS recovery remains unclear. This study investigated the long-term effects of moderate-intensity continuous training (MICT), high-intensity interval training (HIIT), and resistance training (RT) on post-exercise ANS recovery assessed by heart rate variability (HRV) in healthy adults. Methods Three independent cohorts completed 12 weeks of MICT, HIIT, or RT (3 sessions per week). 5-minute continuous HRV data were collected immediately after each session. Recovery slopes of the root mean square of successive differences (RMSSD) and low-frequency/high-frequency power (LF/HF) ratio were calculated. Linear mixed-effects models analyzed trends in recovery slopes across training weeks, with pre-exercise resting HRV and prior-night insomnia score as covariates. Results A total of 43 participants (MICT: n = 13; HIIT: n = 16; RT: n = 14) completed the intervention, yielding 1393 training observations. RMSSD recovery slope decreased significantly in MICT (b=-0.165, P = 0.003), but not in HIIT (b = 0.019, P = 0.680) or RT (b=-0.037, P = 0.452). Between-group comparisons showed a significant difference between HIIT and MICT (Δb = 0.184, P = 0.030). Pre-exercise resting RMSSD (β = 0.022, P < 0.001) and prior-night insomnia score (β = 0.052, P = 0.021) significantly influenced RMSSD recovery slope. No observable trend was detected in LF/HF ratio recovery slopes. Conclusion Long-term training with different exercise modalities differentially affects post-exercise ANS recovery. MICT potentially promotes economical autonomic adaptation; HIIT maintains rapid recovery capacity; RT exerts weaker effects. Pre-exercise resting RMSSD and sleep quality may serve as practical markers for daily training monitoring.