Does firefighters’ physical fitness influence their cardiac parasympathetic reactivation? Analysis with post-exercise heart rate variability and ultra-short-term measures

Abstract

Purpose. This study assessed the influence of firefighters' physical fitness on performances and parasympathetic reactivation in rescue interventions, and tested the validity of post-exercise ultra-short-term heart rate variability. Methods. Twenty-four firefighters were assigned to two groups based on their fitness and performed three simulated interventions. The mean completion time was recorded. The post-exercise root mean square of successive differences of R–R intervals (LnRMSSD) was determined from both criterion (between 5 and 10 min) and ultra-short-term (every 1-min segment from minutes 0–6) analyses. Results. Completion time was better for the highest fitness group in the three simulated interventions while post-exercise LnRMSSD was not influenced by the firefighters' fitness. Reliability between ultra-short-term and criterion analyses differed between the segments tested; minute 5–6 revealed the highest intra-class correlations (0.86–0.97). Concerning sensitivity of both analyses, the criterion analysis revealed differences between the three rescue interventions and the fitness test, but these results were not observed with ultra-short-term measures. Conclusions. Fitness was associated with firefighters’ performances but not with parasympathetic reactivation in the firefighting intervention. The ultra-short-term measures do not seem to be a suitable post-exercise LnRMSSD analysis because of the low sensitivity to reveal differences among exercise conditions.

Keywords:

• vagal
• recovery
• firefighting
• performance

Acknowledgements

The authors would like to thank all of the firefighters for their participation in this study, and for their technical support. They also thank the institutional board of the Service Départemental d’Incendie et de Secours du Doubs for support of the project. The study was part of the European Cross-border Co-operation Programme (Interreg France-Suisse 2014–2020), and was supported by a grant from the European Funding for Regional Development (FEDER).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by European Regional Development Fund [Grant Number Interreg France-Suisse 2014-2020].