Influence of a Training Academy on the Parasympathetic Nervous System Reactivation of Firefighter Recruits—An Observational Cohort Study

• Main Authors: David J. Cornell, Sabrina E. Noel, Xiyuan Zhang, Kyle T. Ebersole
• Format: Article
• Language: English
• Published: MDPI AG 2021-12-01
• Series: International Journal of Environmental Research and Public Health
• Subjects: heart rate recovery; autonomic nervous system function; tactical athletes
• Online Access: https://www.mdpi.com/1660-4601/18/1/109
• ISSN: 1661-7827; 1660-4601

Sudden cardiac death (SCD) is the leading type of line-of-duty death among firefighters. An inability to restore parasympathetic nervous system (PSNS) control after activity is associated with SCD. Post-exercise heart rate recovery (HRR) provides unique insight into reactivation of the PSNS. Thus, the purpose of this study was to examine longitudinal changes in HRR responses of 25 male firefighter recruits. HR data were collected after submaximal exercise at week 1 (W1), week 6 (W6), and week 15 (W15) of their training at an academy. Percent maximal heart rate (%MHR) measures were computed at each HRR time point (%MHR₀, %MHR₁₅, %MHR₃₀, %MHR₄₅, %MHR₆₀, %MHR₁₂₀, %MHR₁₈₀) and absolute HRR values were calculated at 30 s (ΔHRR₃₀), 60 s (ΔHRR₆₀), 120 s (ΔHRR₁₂₀), and 180 s (ΔHRR₁₈₀). After controlling for age and percent body fat, there was no statistically significant interaction between Week × HRR (<i>p</i> = 0.730), and there were no changes in ΔHRR₃₀, ΔHRR₆₀, and ΔHRR₁₂₀, and ΔHRR₁₈₀ indices across time. However, %MHR at W6 and W15 was significantly lower than %MHR at W1 at every HRR time point (<i>p</i>s < 0.001). Therefore, although the firefighter recruit training academy elicited positive training adaptations, changes in PSNS reactivation after submaximal activity were not identified.