Parasympathetic Reactivation Following Maximal Exercise: Influence of Breathwork and Body Composition in ROTC Cadets

Introduction: Autonomic recovery is critical for tactical readiness. While structured breathwork enhances parasympathetic reactivation, it is unclear whether body composition indices such as percent body fat (%BF) or fat-free mass index (FFMI) influence acute recovery following maximal exertion. This study examined whether %BF or FFMI moderate post-exercise autonomic recovery in ROTC cadets. Methods: Fifty-two cadets (age 20.0 ± 3 yrs; %BF 28.5 ± 7.7; FFMI 18.4 ± 2.8) completed a maximal rowing test and were randomized to box breathing (BB, n = 19), cyclic sighing (CS, n = 17), or spontaneous breathing (SB, n = 16) during a 3-min active recovery. HF-HRV was measured at baseline, 1–3 min, and 4–6 min post-exercise. HRR was calculated at 1 and 3 min. Repeated-measures MANOVA and %BF- and FFMI-adjusted MANCOVA were performed. Results: A significant main effect of time was observed for HF-HRV (Pillai’s Trace = .934, F(2,48) = 339.86, p < .001). The Time × Group interaction reached significance in the FFMI-adjusted model (Pillai’s Trace = .190, F(4,96) = 2.52, p = .046). Time × %BF and Time × FFMI interactions were non-significant (p ≥ .271). Regression analyses showed BB and CS predicted higher HF-HRV at Post1 (R² = .193) and Post2 (R² = .224; p ≤ .017), whereas %BF and FFMI were not significant predictors. HRR demonstrated a main effect of time (p < .001) without group or body composition effects. Conclusions: Structured breathwork enhanced post-exercise parasympathetic reactivation independent of %BF and FFMI. Body composition did not significantly influence acute autonomic recovery in this cohort.