Autonomic Nervous System Reactivity During Simulated Cardiopulmonary Resuscitation in Firefighters and Healthcare Workers: Short-term Heart Rate Variability Study

Emergency service personnel work under substantial physical and psychological strain. Heart rate variability (HRV) reflects autonomic reactivity and may serve as a non invasive indicator of occupational load. This study assessed heart rate (HR) and ultra short term HRV responses during simulated cardiopulmonary resuscitation (CPR).A total of 110 participants were enrolled (mean age 25.7 7.9 years; BMI 23.8 3.2 kg/m): 84 emergency healthcare workers (43 women, 41 men) and 26 male firefighters, recruited from two sites (Poland n = 34; Hungary n = 76). The protocol consisted of three consecutive 120 second phases: Pre (rest), During (continuous chest compressions on a Rescue Anne QCPR manikin), and Post (rest). RR intervals were recorded using a Polar H10 sensor (1000 Hz). The primary outcome was RMSSD (ms), with mean HR (bpm) as a secondary measure. Statistical analyses included the Friedman test with Dunn–Bonferroni correction, Mann–Whitney U tests, and Spearman correlations.Mean HR increased from 92.8 23.0 bpm (Pre) to 117.8 18.7 bpm (During) (Δ = +25.0 bpm, +27%, p < 0.001), then decreased to 104.7 22.3 bpm (Post). RMSSD declined from 23 ms (IQR 16–33) to 19.5 ms (12–27) (Δ = −3.5 ms, −15%, p = 0.001), with partial recovery to 20 ms (15–28) (Pre vs Post phase). HR varied by age, BMI, and sex across multiple phases (e.g., mean HR: all phases p < 0.01). RMSSD differed by sex During and Post (p = 0.031 and p = 0.012), but not by age or BMI (all p ≥ 0.07). No monotonic association was found between mean HR and mean HRV within phases (|ρ| ≤ 0.056, p ≥ 0.559).Simulated CPR induced marked tachycardia and a short term reduction in RMSSD, indicating acute sympathetic activation with partial recovery afterward. Ultra short term HRV monitoring using wearable devices appears feasible in both training and operational contexts and may serve as an early marker of excessive psychophysical load. Incorporating HRV metrics into occupational health protocols could support risk stratification, targeted conditioning and recovery strategies, and enhance safety among emergency personnel.