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Prolonged work in hot environments leads to progressive water and electrolyte loss from the body. The rate of sweating varies among individuals and depends on the environmental conditions, but in protective clothing and very hot environments rates can reach 2.25 L/hour. Because hypohydration will impair work performance and increases the risk of heat injury, consumption of fluids is necessary to prevent dehydration and enhance performance. Much of the research on rehydration has been conducted in athletic settings. The purpose of this review is to interpret the existing research literature on hydration in a way that is useful to industrial hygienists and safety experts. The authors hope to provide industrial hygienists and safety professionals with scientific bases for making recommendations regarding beverage availability and hydration practices. Although water is a very common beverage, some previous research has reported that drinks containing low to moderate levels of electrolytes and carbohydrates may provide some significant advantages in industrial situations. In general these studies seem to support the use of electrolyte-carbohydrate beverages as a supplement to water or as a replacement for water.

This study examined the effects of ingesting beverages of varying electrolyte-carbohydrate (ECHO) composition on hydration, sensory response, physiological function, and work performance during 4 hours of simulated industrial work for subjects wearing impermeable protective clothing (PC). Male subjects (N=18) completed four separate work sessions. Each session consisted of 30 min of treadmill walking with intermittent arm curls at 300 kcal per hour (moderate work rate), followed by 30 min of rest, for a total of 4 hours at 33 degrees C wet-bulb globe temperature. Excessive physiological strain prevented only four subjects from completing the 4-hour protocol. A different beverage was provided for consumption ad libitum for each work trial in a repeated measures, double-blind design. The beverages included lime colored water (W), lemon-lime placebo (P), lemon-lime ECHO with 18 mEq/L NaCl (ECHO18), and lemon-lime ECHO with 36 mEq/L NaCl (ECHO36). There was no difference in sweat production among the four trials (p = 0.61). Mean (standard deviation [SD]) fluid consumption was significantly greater for the ECHO36 [771 (+/-264) mL per hour] as compared with the W [630.6 (+/-234) mL per hour] and the P [655.2 (+/-228) mL per hour] (p<0.05), but not significantly greater than the ECHO18 [740.4 (+/-198) mL per hour]. Also, consumption of the ECHO18 was significantly greater than the W. Mean (SD) weight change, expressed as a percentage of total body weight (pre minus post), was -0.55(+/-0.8) for W, -0.31(+/-1.0) for P, -0.01(+/-1.1) for ECHO18, and +0.11(+/-1.1) for ECHO36 (p = 0.06). Subjects drank less and tended to experience greater weight loss in trials in which W or P were provided compared with trials in which either ECHO was provided. Thus, ECHO beverages, when provided ad libitum to workers wearing PC in a hot environment, produced better hydration than water.