SEASONAL CHANGES IN CARDIOVASCULAR FUNCTION, RISK FACTORS, AND OXIDATIVE STRESS OF WILDLAND FIREFIGHTERS

C.M. Williamson-Reisdorph, K.S. Christison, S.C. Gurney, K.G.S. Tiemessen, J.A. Sol, T.S. Quindry, C.G. Palmer, M.W. Bundle, C.L. Dumke, FACSM, J.C. Quindry, FACSM University of Montana, Missoula, MT Wildland firefighters (WLFF) experience extreme physiological strain throughout a typical season due to intense occupational demands and consistent woodsmoke exposure. There is a rationale to indicate that accumulated physiological strain, and oxidative stress, throughout a WLFF season has the potential to negatively alter cardiovascular function and risk factors. PURPOSE: The purpose of the study was to examine the effects of a season on cardiovascular function, risk factors, and markers of oxidative stress in WLFF. METHODS: Fourteen members of a Type I interagency hotshot crew participated in the study (males: n=13, females: n=1, age: 30.1 years ± 4.8). Pre- and post-seasonal resting measurements (May, October) were obtained for heart rate variability (lnRMSSD, lnHF, lnHF, LF:HF), pulse wave velocity (PWV), blood lipid panels (TC, TG, LDL, HDL), metabolic biomarkers (blood glucose, HbA1c), blood pressure (SBP, DBP) and blood oxidative stress (3-nitrotyrosine, 8-isoprostane, lipid hydroperoxides). Paired samples t-tests were used to identify differences among pre- and post- seasonal values. RESULTS: There were no seasonal effects observed on resting heart rate variability, PWV, 3-nitrotyrosine, 8-isoprostane, TC, TG, LDL, blood glucose, SBP, or DBP (p\u3e0.05). A significant reduction occurred in HDL (Pre: 53 mg/dL ± 14, Post: 45 mg/dL ± 18, p=0.043) and both HbA1c (Pre: 5.2% ± 0.2 , Post: 5.3% ± 0.2, p=0.034) and lipid hydroperoxides (Pre: 2.5 ± 0.5, Post: 4.9 ± 0.6, p = 0.003 ) increased from pre- to post-season. CONCLUSION: These data suggest a WLFF season did not impact resting markers of heart rate variability, pulse wave velocity, 3-nitrotyrosine, and 8-isoprostane. Alterations in metabolic biomarkers of cardiovascular risk factors (HDL and HbA1c) and lipid hydroperoxides demonstrate unfavorable seasonal changes, suggesting that the WLFF season may increase cardiovascular risk. Funded by the USFS 16-CR-11138200-005

METABOLIC AND CARDIOVASCULAR ALTERATIONS DURING CRITICAL TRAINING IN WILDLAND FIREFIGHTERS

S.C. Gurney, K.S. Christison, C.M. Williamson-Reisdorph, K.G.S. Tiemessen, J.A. Sol, T.S. Quindry, M.W. Bundle, C.G. Palmer, J.C. Quindry, FACSM, C.L. Dumke, FACSM University of Montana, Missoula, MT Wildland firefighters (WLFF) are confronted with numerous physical and mental stressors. Pre-fire season includes an intense 2- week critical training (CT) period; a preparatory phase that can result in injury, illness, and rhabdomyolysis. PURPOSE: To identify physiologic changes in metabolic biomarkers that occur during 2 weeks of CT in WLFF. METHODS: Eighteen male (29.4±1.1 yr, 182.1±1.6 cm) and three female (26.7±2.6 yr, 169.5±4.2 cm) participants were recruited from a Type I interagency hotshot fire crew and monitored over their 2-week CT. Fitness was assessed via BLM Fitness Challenge (push-ups, pull- ups, sit-ups, 1.5 mi run). Subjects were asked to fast and abstain from caffeine for blood draws on days 1, 4, 8, and 11. Plasma was analyzed for changes in the metabolic profile and oxidative stress markers 3-Nitrotyrosine (3NT), 8-Isoprostane (8ISO), and Lipid Hydroperoxides (LOOH). A one-way repeated measures ANOVA was used to analyze 8ISO, 3NT, and LOOH. Paired samples t-tests were used to compare metabolic biomarkers. Data presented as mean±SEM. RESULTS: CT elicited decrease in total cholesterol (TC) (173.6±12.1 to 153.4±8.6 mg·dL-1, p=0.01), hemoglobin A1c (5.2±0.1 5.1±0.1 %, p=0.003), hemoglobin (15.5±0.4 to 14.3±0.3 g·dL- 1, p=0.003), and estimated plasma volume to (53.8±0.7 to 50.7±1.4 %, p=0.005) from day 1 to 11. No difference was observed in high- density lipoprotein cholesterol. A main effect for time was observed in 8ISO (p- 1). 3NT was significantly elevated from day 4 to day 8 (d4: 2.4±0.6, d8: 2.9±0.6 mg·mL-1). LOOH showed a significant increase across all days (d1: 2.2±0.4, d4: 2.8±0.5, d8: 3.4±0.5, d11: 4.0±0.6 mM). Fitness was significantly correlated with DTC (r=0.58, p=0.046) and D8ISO (r=0.60, p=0.050). CONCLUSION: These data suggest the exertion required of WLFF during CT results in positive alterations to the metabolic profile. The changes in oxidative stress markers may reflect rapid adaptation to the CT stressors. These data suggest that WLFF are able to adapt quickly to the physical stress of CT, where fitness may be a protector of metabolic perturbations. Funded by the US Forest Service 16-CR-11138200-005