Effects of an electrolyte additive on hydration and drinking behavior during wildfire suppression.

OBJECTIVE: The purpose of this study was to compare the effects of a water + electrolyte solution versus plain water on changes in drinking behaviors, hydration status, and body temperatures during wildfire suppression. METHODS: Eight participants consumed plain water, and eight participants consumed water plus an electrolyte additive during 15 hours of wildfire suppression. Participants wore a specially outfitted backpack hydration system equipped with a digital flow meter system affixed inline to measure drinking characteristics (drinking frequency and volume). Body weight and urine-specific gravity were collected pre- and postshift. Ambient, core, and skin temperatures were measured continuously using a wireless system. Work output was monitored using accelerometry. RESULTS: There were no differences between groups for body weight, drinking frequency, temperature data, activity, or urine-specific gravity (1.019 +/- 0.007 to 1.023 +/- 0.010 vs. 1.019 +/- 0.005 to 1.024 +/- 0.009 for water and water + electrolyte groups pre- and postshift, respectively; P < .05). There was a main effect for time for body weight, demonstrating an overall decrease (78.1 +/- 13.3 and 77.3 +/- 13.3 kg pre- and postshift, respectively; P < .05) across the work shift. The water group consumed more total fluid (main effect for treatment) than the water + electrolyte group (504 +/- 472 vs. 285 +/- 279 mL.h(-1) for the water and water + electrolyte groups, respectively; P < .05). CONCLUSION: The addition of an electrolyte mixture to plain water decreased the overall fluid consumption of the water + electrolyte group by 220 mL.h(-1) (3.3 L.d(-1)). Supplementing water with electrolytes can reduce the amount of fluid necessary to consume and transport during extended activity. This can minimize carrying excessive weight, possibly reducing fatigue during extended exercise.

Supplemental feedings increase self-selected work output during wildfire suppression.

PURPOSE: The purpose of this study was to determine the impact of supplemental feeding strategies on self-selected activity during wildland fire suppression. METHODS: Seventy-six wildland firefighters were studied in three experiments for three fire seasons. During the first two seasons, subjects consumed, in addition to their sack lunch, 1) liquid carbohydrate (CHO) (200 mL.h, 20% CHO (40 g.h, 160 kcal.h)) or placebo (PLA) every hour, or 2) liquid CHO (200 mL.h, 20% CHO (40 g.h, 160 kcal.h) every even hour and solid CHO (25 g of CHO, 10 g of protein, 2 g of fat, and 160 kcal.h) every odd hour, or PLA, using counterbalanced crossover designs. During the third season, subjects consumed their sack lunch halfway through their workday, or shift food items of approximately 150-400 kcal at 90-min intervals after breakfast in a randomized crossover design (isocaloric intake, 1534+/-265 kcal per workday). Work output was monitored using CSA and MiniMitter actigraphy units. RESULTS: During the liquid CHO trials, subjects consuming CHO demonstrated significantly higher average activity counts throughout the day compared with PLA (50,262+/-36,560 and 40,159+/-35,969 counts per hour for 12 h for the CHO and PLA trials, respectively; P<0.05). For the liquid+solid CHO trials, subjects consuming CHO demonstrated higher average activity counts per minute 2 h before lunch and the last 4 h of the workday compared with PLA (P<0.05). For the sack lunch and shift food trials, subjects consuming shift foods demonstrated higher average counts per minute during the final 2 h compared with those consuming sack lunch (521+/-421 vs 366+/-249 counts per minute during 2 h; P<0.05). CONCLUSION: Liquid and/or solid supplemental CHO and regular feedings increased self-selected work rates during wildland fire suppression, particularly during the latter hours of the workday.