The Effect Of Heat On Heart Rate Variability During Exercise In Male Firefighters

Abstract

Central vascular function (stiffness, pressure wave energy transmission, hemodynamics) can impact high-flow end-organs such as the myocardium. Police officers, firefighters, emergency medical services personnel, and military personnel ("emergency responders" [ER]) experience more on-duty deaths from cardiac events than other occupational groups. As ER face unique occupational stressors, central vascular stress reactivity (CVSR) may contribute to cardiac risk. PURPOSE: Determine if ER have greater CVSR compared with non-ER (NER). METHODS: 9 ER and 9 age-, sex-, race-, and body fat-matched NER (n = 2 women; Table 1) had central vascular function assessed at rest and during 3 min of mental stress (Stroop). Potential covariates included: fasting cholesterol, lipids, and glucose from a fingerstick sample; physical activity via the International Physical Activity Questionnaire (IPAQ); and depressive symptomology from the Center for Epidemiologic Studies Depression Scale (CESD). Aortic stiffness was assessed using carotid-femoral pulse wave velocity. Doppler ultrasound was used to measure carotid artery β stiffness, while Wave Intensity Analysis provided measures of pressure wave energy transmission. Carotid pressures were measured using applanation tonometry. CVSR was calculated as mental stress -resting. RESULTS: Groups had similar metabolic profiles and IPAQ scores (p ≥ 0.11). CESD score was greater in ER than NER (p = 0.04) and was used as a covariate for analyses. CVSR was similar between groups for all variables (p > 0.05; Table 1). CONCLUSIONS: Despite more depressive symptomology, ER do not have greater central vascular function changes to stress compared with NER, suggesting high resiliency during mental stress in ER.