Change in heart rate variability during two firefighting work cycles

Abstract

This study aimed to determine whether the change in heart rate variability from pre to post firefighting is modulated by different work cycles. Thirteen male firefighters underwent two firefighting simulations that comprised two identical 25-min work bouts intercalated by a passive recovery period of either 20 min (T20) or 5 min (T5). The square root of the mean squared differences of successive R–R intervals (RMSSD) and aural temperature were measured at rest before (PRE) and after (POST) firefighting simulations. The decrease in RMSSD was different between firefighting simulations (T20: −10 ± 21.2 ms, T5: −19.9 ± 20.9 ms, interaction, p = 0.02). Post-firefighting aural temperature was greater (p = 0.05) in T5 (37.18 ± 0.53 °C) than in T20 (36.88 ± 0.49 °C). In conclusion, a shorter recovery period of 5 min between firefighting work bouts decreases post-firefighting heart rate variability, possibly attributed to a lower parasympathetic reactivation and a higher absolute value of body temperature.

KEYWORDS:

• firefighter
• autonomic
• cardiac
• parasympathetic
• body temperature
• rehabilitation

Acknowledgements

P.G. was supported by a doctoral research scholarship from Fonds de recherche du Québec – Santé. The authors thank Magali Brousseau-Foley, MD for the medical follow-up of the participants. They are also grateful to the Service de sécurité incendie de Trois-Rivières for providing all personal protective equipment (PPE) and encouraging their firefighters to participate in this study, to the union of the Service de sécurité incendie de Trois-Rivières for encouraging their members to participate in this study, to the Service de sécurité incendie de Shawinigan for providing the tools and test equipment and to Protection Incendie CFS Ltée for providing the self-contained breathing apparatus. Finally, thanks are due to all participants who volunteered in this study.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by Fonds de Recherche du Québec - Santé.