Sweat rate and sodium loss during work in the heat

Graham P Bates,Veronica S Miller

doi:10.1186/1745-6673-3-4

Graham P Bates, Veronica S Miller

Open Access

https://doi.org/10.1186/1745-6673-3-4

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Abstract

ObjectiveSignificant and poorly documented electrolyte losses result from prolonged sweating. This study aimed to quantify likely sodium losses during work in heat.MethodsMale subjects exercised in an environmental chamber on two consecutive days in both winter and summer. Sweat collecting devices were attached to the upper arms and legs.ResultsSweat rates were higher and sodium concentrations were lower in the summer (acclimatised) than the winter (unacclimatised) trials. Sweat sodium concentration was reduced on the second day in summer but not winter. Regional differences were found in both seasons.ConclusionThe difference between days in summer probably reflects short-term acclimation. The difference between seasons reflects acclimatisation. The data predict average sodium (Na) losses over a work shift of 4.8–6 g, equivalent to 10–15 g salt (NaCl). Losses are potentially greater in unacclimatised individuals.Fluid and electrolyte losses resulting from prolonged sweating must be replaced to prevent imbalance in body fluids, however guidelines for this replacement are often conflicting.This study provides important information for occupational health practitioners by quantifying the likely sodium losses over a work shift and providing recommendations for replacement.

Highlights

During prolonged work periods in the heat (8–12 hour shifts), the maintenance of high sweat rates leads to progressive dehydration, which may be accompanied by impairment of mental and physical performance and of heat dissipation [1,2,3,4]
Fluid and electrolyte losses resulting from prolonged sweating must be replaced to prevent imbalance in body fluids, guidelines for this replacement are often conflicting
This study provides important information for occupational health practitioners by quantifying the likely sodium losses over a work shift and providing recommendations for replacement

Summary

Introduction

During prolonged work periods in the heat (8–12 hour shifts), the maintenance of high sweat rates leads to progressive dehydration, which may be accompanied by impairment of mental and physical performance and of heat dissipation [1,2,3,4]. Dehydration will impair work capacity and may pose a serious risk to health [5]; the intake of fluid during the working period to replace sweat losses is imperative. The sodium replacement need is often overlooked, mainly as a consequence of scant information regarding the sweat loss of sodium over time. With a better understanding of electrolyte loss in sweat, accurate advice regarding replacement beverages can be provided to workers performing manual tasks in the heat. Sodium is added to some drinks for the purpose of replacing sweat salt losses, and to aid in the transport of glucose across the (page number not for citation purposes)

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