Objective: Document wildland firefighters (WLFFs) hydration status during a singular workshift (13.7 AE 1.4 hours). Methods: WLFF researchers documented real-time WLFF (n ¼ 71) urine metrics and fluid consumption. Body weight and blood samples (n ¼ 25) were also collected. Two-tailed dependent t tests determined statistical significance (P < 0.05). Results: Body weight significantly decreased (À0.3 AE 1.1%, P > 0.05). Fluid consumption totaled 6.2 AE 2.3 L including food and 5.0 AE 2.1 L without food. Morning versus afternoon urine frequency (2.6 AE 1.3, 3.1 AE 1.9 voids), urine volume (1.2 AE 0.7, 1.3 AE 0.8 L), urine volume per void (440 AE 157, 397 AE 142 mL), and urine specific gravity (1.010 AE 0.007, 1.010 AE 0.007) were not significantly different (P > 0.05). Pre-to post-workshift serum chloride (103.2 AE 1.9, 101.4 AE 1.7 mM) and blood glucose (5.2 AE 0.4, 4.5 AE 0.7 mM) significantly decreased (P < 0.05), while serum sodium (141.5 AE 2.4, 140.8 AE 2.0 mM) and serum potassium (4.3 AE 0.3, 4.2 AE 0.3 mM) remained stable (P > 0.05). Conclusions: WLFFs can ingest fluid and food amounts that maintain workshift euhydration and electrolyte status.

Introduction-Wildfire suppression is characterized by high total energy expenditure and water turnover rates. Hydration position stands outside 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 (preand 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.

Despite high levels of physical activity amongst wildland firefighters on standard assignments, maladaptive changes in serum lipids and adipose tissue present in this cohort over a season of wildfire suppression. Therefore, the commonly known benefits of exercise may be negatively affected by the multifactorial stressors of this occupation.