Deterioration of Lipid Metabolism Despite Fitness Improvements in Wildland Firefighters.

OBJECTIVE: Determine serum lipid and general health/fitness alterations following a 5-month wildfire suppression season. METHODS: We recruited 100 wildland firefighters (WLFFs) to a 5-month pre- to post-season observational study. Nude body mass, blood pressure (BP), grip strength, and steptest heart rate (HR) were recorded. Blood samples were collected for lipid panel analysis (total cholesterol, high density lipoproteins (HDL)-cholesterol, low density lipoproteins-cholesterol, very low density lipoproteinscholesterol, triglycerides, triglyceride:HDL-cholesterol ratio). Two-tailed dependent t tests determined statistical significance (P < 0.05). RESULTS: There were pre- to post-season changes in nude body mass (+2 ±â€Š4%, P  = 0.001), systolic BP (-2 ±â€Š10%, P  = 0.01), step-test HR (-5 ±â€Š10%, P  < 0.001), and all serum lipids (total cholesterol: +5 ±â€Š14%, P  = 0.02, HDL-cholesterol: = 1 ±â€Š17%, P  = 0.04, low density lipoproteins-cholesterol: +8 ±â€Š22%, P  = 0.02, very low density lipoproteins-cholesterol: +31 ±â€Š49%, P  < 0.001, triglycerides: +30 ±â€Š49%, P  < 0.001, triglyceride:HDL-cholesterol ratio: +37 ±â€Š58%, P  < 0.001). Pre- to post-season diastolic BP (P = 0.12) and grip strength (P = 0.60) remained stable. CONCLUSIONS: WLFFs demonstrate maladaptive serum lipids and body mass alterations despite subtle aerobic fitness improvements.

Workshift Changes in Hydration Status During Wildfire Suppression.

OBJECTIVE: Document wildland firefighters (WLFFs) hydration status during a singular workshift (13.7 ±â€Š1.4 hours). METHODS: WLFF researchers documented real-time WLFF (n = 71) urine metrics and fluid consumption. Body weight and blood samples (n = 25) were also collected. Two-tailed dependent t tests determined statistical significance (P < 0.05). RESULTS: Body weight significantly decreased (-0.3 ±â€Š1.1%, P > 0.05). Fluid consumption totaled 6.2 ±â€Š2.3 L including food and 5.0 ±â€Š2.1 L without food. Morning versus afternoon urine frequency (2.6 ±â€Š1.3, 3.1 ±â€Š1.9 voids), urine volume (1.2 ±â€Š0.7, 1.3 ±â€Š0.8 L), urine volume per void (440 ±â€Š157, 397 ±â€Š142 mL), and urine specific gravity (1.010 ±â€Š0.007, 1.010 ±â€Š0.007) were not significantly different (P > 0.05). Pre- to post-workshift serum chloride (103.2 ±â€Š1.9, 101.4 ±â€Š1.7 mM) and blood glucose (5.2 ±â€Š0.4, 4.5 ±â€Š0.7 mM) significantly decreased (P < 0.05), while serum sodium (141.5 ±â€Š2.4, 140.8 ±â€Š2.0 mM) and serum potassium (4.3 ±â€Š0.3, 4.2 ±â€Š0.3 mM) remained stable (P > 0.05). CONCLUSIONS: WLFFs can ingest fluid and food amounts that maintain workshift euhydration and electrolyte status.

Influence of Fluid Delivery Schedule and Composition on Fluid Balance, Physiologic Strain, and Substrate Use in the Heat.

INTRODUCTION: Wildfire suppression is characterized by high total energy expenditure and water turnover rates. Hydration position stands outline hourly fluid intake rates. However, dose interval remains ambiguous. We aimed to determine the effects of microdosing and bolus-dosing water and microdosing and bolus-dosing carbohydrate-electrolyte solutions on fluid balance, heat stress (physiologic strain index [PSI]), and carbohydrate oxidation during extended thermal exercise. METHODS: In a repeated-measures cross-over design, subjects completed four 120-min treadmill trials (1.3 m·s-1, 5% grade, 33°C, 30% relative humidity) wearing a US Forest Service wildland firefighter uniform and a 15-kg pack. Fluid delivery approximated losses calculated from a pre-experiment familiarization trial, providing 22 doses·h-1 or 1 dose·h-1 (46±11, 1005±245 mL·dose-1). Body weight (pre- and postexercise) and urine volume (pre-, during, and postexercise) were recorded. Heart rate, rectal temperature, skin temperature, and steady-state expired air samples were recorded throughout exercise. Statistical significance (P<0.05) was determined via repeated-measures analysis of variance. RESULTS: Total body weight loss (n=11, -0.6±0.3 kg, P>0.05) and cumulative urine output (n=11, 677±440 mL, P>0.05) were not different across trials. The micro-dosed carbohydrate-electrolyte trial sweat rate was lower than that of the bolus-dosed carbohydrate-electrolyte, bolus-dosed water, and microdosed water trials (n=11, 0.8±0.2, 0.9±0.2, 0.9±0.2, 0.9±0.2 L·h-1, respectively; P<0.05). PSI was lower at 60 than 120 min (n=12, 3.6±0.7 and 4.5±0.9, respectively; P<0.05), with no differences across trials. The carbohydrate-electrolyte trial's carbohydrate oxidation was higher than water trial's (n=12, 1.5±0.3 and 0.8±0.2 g·min-1, respectively; P<0.05), with no dosing style differences. CONCLUSIONS: Equal-volume diverse fluid delivery schedules did not affect fluid balance, PSI, or carbohydrate oxidation during extended thermal work.