Wildland fire suppression presents a working environment that often exceeds an energy expenditure of 20 MJ/day. Despite high levels of chronic physical exertion, we have noted maladaptive alterations in adiposity and blood lipids in a small cohort of wildland firefighters (WLFF) over a short 3-month season.
PURPOSE: To determine changes in clinical health metrics and serum lipids resulting from 5 months of seasonal wildland fire suppression.
METHODS: We recruited 79 WLFF (72 males and 7 females from six crews (5 Hotshot crews, 1 Initial Attack crew) based in MT and CA and conducted a pre- and post-season observational study. After an overnight fast, nude body mass, blood pressure (BP), grip strength, and a step test (~VO2=20.7 mL/kg/min) for heart rate (HR) steady state were recorded. Blood samples were collected and analyzed for serum total cholesterol (CHOL), high density lipoprotein (HDL), low density lipoprotein (LDL), very low-density lipoprotein (VLDL), and triglycerides (TRIG). A 2-tailed dependent t-test was used to compare pre- and post-season values. Statistical significance was established at p<0.05.
RESULTS: Body mass was increased (pre 77.4±9.7 vs post 78.4±9.5 kg, p<0.01). Systolic and diastolic BP decreased (pre 133±13/76±10 vs post 128±14/73±9 mmHG, p<0.001 and 0.05, respectively). Grip strength remained unchanged (pre 56.3±10.7 vs post 56.3±11.4 kg, p>0.05). There was a decrease in the HR response during the step test (pre 102±13 vs post 96±9 BPM, p<0.001). Serum CHOL and LDL did not change over the season (p>0.05). In contrast, serum TRIG (pre 73±35 vs post 92±55 mg/dl, p<0.0001) and VLDL (pre 14±7 vs post 18±11 mg/dl, p<0.0001) were significantly increased by the end of the season, p<0.001. Similarly, HDL was significantly reduced (pre 68±15 vs post 64±13 mg/dl), corresponding to an increase in the TC/HDL ratio (pre 1.2±0.8 vs post 1.6±1.3 (p<0.0001).
CONCLUSIONS: Despite favorable changes in BP and aerobic fitness, there were maladaptive changes in serum lipids that occurred in conjunction with an increase in body mass. Further studies should explore the influence of diet, mental/emotional stress, and/or smoke exposure on the mechanisms responsible for the dysregulation of lipid metabolism in WLFF. Supported by the United States Forest Service, National Technology and Development Program