Firefighters’ basal cardiac autonomic function and its associations with cardiorespiratory fitness

Issue title: Special Section: Firefighters

Article type: Research Article

Authors: Porto, Luiz Guilherme G.^{a; b; c; d; *; 1} | Schmidt, Ana Clara Bernardes^e | de Souza, Jessica Maximo^e | Nogueira, Rosenkranz Maciel^{a; f} | Fontana, Keila E.^a | Molina, Guilherme E.^{a; c; 3} | Korre, Maria^{d; g} | Smith, Denise L.^g | Junqueira Jr., Luiz Fernando^{h; 2} | Kales, Stefanos N.^d

Affiliations: [a] Faculty of Physical Education of the University of Brasilia, Campus Darcy Ribeiro, Brasilia, DF, Brazil | [b] Scholarship from the Conselho Nacional de Desenvolvimento Cientifico e Tecnologico, CNPq, Brazil | [c] Cardiovascular Laboratory of the Faculty of Medicine, University of Brasilia, DF, Brazil, Campus Darcy Ribeiro, Brasilia, DF, Brazil | [d] Environmental and Occupational Medicine and Epidemiology Program, Department of Environmental Health, Harvard T. H. Chan School of Public Health, Boston, MA, USA | [e] Physiotherapy Course, Faculty of Ceilandia, University of Brasilia, Campus Ceilândia, Brasilia, DF, Brazil | [f] Federal District (Brasilia) Military Firefighter Brigade, CBMDF, SAM lote D, modulo E, Brasilia, Brazil | [g] Health and Human Physiological Sciences Department, Skidmore College, Saratoga Springs, NY, USA | [h] Cardiology Division, Clinical Medicine Area, Cardiovascular Laboratory of the Faculty of Medicine, University of Brasilia, Brasilia, DF, Brazil

Correspondence: [*] Address for correspondence: Luiz Guilherme Grossi Porto, Department of Environmental Health, Harvard T. H. Chan School of Public Health, 677 Huntington Ave, 14th floor, Boston, MA 02115, USA. Tel.: +1 55 61 99973 7141; Fax: +1 617 432 3441; E-mail: lgporto@hsph.harvard.edu and luizggporto@gmail.com.

Note: [1] ORCID: Luiz Guilherme G. Porto: ORCID: 0000-0002-6240-1614.

Note: [2] ORCID: Luiz Fernando Junqueira Jr: ORCID: 0000-0002-5786-2969.

Note: [3] ORCID: Guilherme E. Molina: ORCID: 0000-0002-5937-079X.

Abstract: BACKGROUND:Firefighters’ activities require constant adjustments of the cardiovascular system with cardiac autonomic function (CAF) playing an important role. Despite the crucial role of CAF in regulating stress response, little is known about firefighters’ CAF. OBJECTIVE:We aimed to characterize the resting on-duty and off-duty CAF of male firefighters, in association with cardiorespiratory fitness (CRF). METHODS:We evaluated 38 firefighters in an on-duty rest condition and 26 firefighters in an off-duty laboratory-controlled condition. CAF was addressed by means of heart rate variability (HRV). We compared HRV measurements between CRF categories (<12METs vs ≥12METs). Wilcoxon, Mann-Whitney texts and Spearman correlation were used and General Linear Model was applied for age and BMI adjustments. RESULTS:Firefighters’ resting CAF is characterized by a predominant sympathetic modulation and a large inter-individual dispersion in all HRV indices, in both groups. We found a positive correlation between a higher CRF, the overall CAF and the higher parasympathetic activity (p <  0,03). Firefighters with CRF ≥12 METs showed a higher parasympathetic modulation. CONCLUSIONS:Firefighters’ resting CAF is characterized by a predominant sympathetic modulation and a large inter-individual dispersion in all HRV indices, in both groups. Our results support mandatory physical training focused in improving firefighters’ CAF as a cardiopretective effect.

Keywords: Firefighting; autonomic nervous system; sympathovagal balance; physical fitness; occupational cardiovascular risk

DOI: 10.3233/WOR-192883

Journal: Work, vol. 62, no. 3, pp. 485-495, 2019