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 ail 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 work shift. The water group and 77.3 +/- 13.3 kg pre- and postshift. respectively: P <.05) across the consumed more total fluid (main effect for treatment) than the water + electrolyte group (504 +/- 472 vs. 295 +/- 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.

Wild land firefighters (WLFF) work long shifts in extreme environmental conditions. Temperature regulation and hydration status are important factors that can effect the WLFF cognitive and physical performance. PURPOSE The purpose of this investigation was to determine the effects of wildfire suppression on temperature regulation and drinking behaviors during an arduous day on the fireline. METHODS Subjects included male (n=16) and female (n=4) wildland firefighters from various Hot Shot and District crews. Core, skin and ambient temperature and self-selected work rate (via activity monitor) were measured using a wireless physiological monitoring system. Drinking characteristics were recorded with a previously validated digital flow meter (MSSE 33(5):S257, 2001), which allowed for the measures drink volume/rate (ml/hr), drink frequency (drinks/hour), and total volume (L/workshift). Urine specific gravity was measured at 2nd AM void, late AM, late afternoon, and post shift +1hr. Data were analyzed across the day by comparing average AM and PM workshift values with repeated measures ANOVA. RESULTS Ambient temperature demonstrated a significant increase throughout the day (AM=24.8Ã'±2.2 and PM=34.0Ã'±3.4 Ã〈Å°C, p<0.05). There was also a significant increase in core (AM=37.2Ã'±0.3, PM=37.8Ã'±0.02), p<0.05) and skin (AM=32.7Ã'±1.2, PM=34.67Ã'±1.3, p<0.05) temperatures throughout the day. Drinking volume (ml/hour) was significantly higher during hours 8–15 vs. hours 1–7 (AM=275Ã'±139, PM=583Ã'±259, p<0.05). There was asignificant decrease in nude body weight pre to post-shift (AM=79.8Ã'±14.1, PM=79.1Ã'±14.2, p <0.05). Similarly, urine specific gravity demonstrated a significant increase throughout the workshift (AM=1.019Ã'±0.006, PM=1.023Ã'±0.009, p<0.05). However, self-selected workrate (mean activity counts/hr) was not significantly different between the early and later segments of the workshift (AM=502Ã'±223, PM=450Ã'±146, p>0.05). CONCLUSION These data demonstrate that extended arduous work in the heat is associated with a rise in ambient, core and skin temperature and self-selected drinking volume. The similarity in hourly activity counts during the early and later segments of the workshift suggests that drinking behavior may be more related to temperature changes than work rate. The reduction in BW and increase in urine SG suggests that although drinking volume increased throughout the day, it was not enough to maintain euhydration.

Our laboratory has recently demonstrated a mean rate of water turnover of (95±20 ml.kg-1.24 h-1) in elite wildland firefighters exposed to five days of extended work shifts (MSSE 35(10):176–65, 2003). PURPOSE This study evaluated the effects of water (W) or water+supplemental electrolytes (W+E) on core body temperature, self-selected work, hydration, and drinking behavior during arduous wildfire suppression. METHODOLOGY Subjects included male (n=16) and female (n=4) wildland firefighters from various Hot Shot and District crews during the 2004 Fischer fire. Subjects were randomly placed into W (n=10), which consumed water only during the entire workshift or a W+E (n=10). The W+E group consumed water that included an electrolyte additive (45 mg Magnesium, 125 mg Sodium, 390 mg Chloride, 130 mg Potassium, and 20 mg Sulfate per liter). Each subject was outfitted with a wireless data recording system for continuous measurement of core, skin, and ambient temperature and self-selected activity (Mini Mitter activity monitor). Nude body weight was recorded pre and post workshift. Urine specific gravity was measured at 2nd AM void, late AM, late afternoon, and post shift + 1hr. Drinking behavior was measured with a previously validated drinking reservoir system (MSSE 33(5):S257, 2001). Data was analyzed using a mixed design ANOVA with repeated measures. RESULTS The overall change in nude body weight showed a significant decrease across the workshift (79.8 and 79.1 kg for pre and post shift values, respectively) for the entire group (N=20). There were no differences between the two groups (Pre=79.8±16.6, Post=79.4±16.3 kg and Pre=78.0±12.1, Post=77.1±12.5 kg for W and W+E, respectively). There were no differences between the groups in ambient, core or skin temperature throughout the day. Average hourly self-selected work rate via activity monitor data was similar for both groups (439±341 and 487±341 counts.hr-1 for the W and W+E, respectively). Urine specific gravity was significantly increased across the workshift in the W+E group (1.019±0.007 and 1.025±0.008 for AM and PM samples, respectively). However, urine specific gravity was unchanged in the W group (1.019±0.004 and 1.021±0.011 for AM and PM samples, respectively). Total drinking volume was significantly higher for the W group (7.5±2.3 and 4.3±1.8 L for the W and W+E, respectively). CONCLUSION Based on the disparity in drinking volume and the similarity in weight loss, these data indicate that W+E consumption may act to preserve total body water during arduous work in extreme environments when access to water may otherwise be limited.