Macie Tarr
Macie Tarr is a senior studying Epidemiology at Indiana University with a passion for research in chronic disease, disease equity, and occupational health. Upon graduation, she will be pursuing her MPH in Epidemiology from Tulane University.
Voluntary drinking prevents dehydration when following occupational heat stress recommendations
Macie L. Tarr1, Hayden W. Hess1, Tyler B. Baker1, David Hostler2, Zachary J. Schlader1
1Indiana University – Bloomington, Indiana, USA
2University at Buffalo, NY, USA
Introduction: The National Institute for Occupational Safety and Health [NIOSH] issues guidance that aim to maintain core temperature below 38.0°C and prevent dehydration [>2% body mass loss] in workers exposed to heat. Hydration recommendations suggest drinking 237 mL of a cool sport drink every 15-20 min based on the premise that ad libitum drinking results in dehydration due to inadequate drinking, but this has never been examined during recommendation compliant work. Therefore, we tested the hypothesis that ad libitum drinking during heat stress recommendation compliant work will result in >2% body mass loss.
Methods: Nine healthy subjects (4 female) completed four trials consisting of 4 h of exposure to wet bulb globe temperatures (WBGT) of 24.1±0.3°C (A), 26.6±0.2°C (B), 28.5±0.2°C (C), 29.8±1.7°C (D). Subjects walked on a treadmill and work-rest ratios were prescribed as a function of WBGT [work:rest per hour - A: 60:0, B: 45:15, C: 30:30, D: 15:45]. Subjects were provided 237 mL of a cool sport drink every 15 min and drank ad libitum. Body mass loss was determined from changes in nude body mass.
Results: In line with NIOSH guidelines, subjects maintained an average core temperature below 38.0°C in all trials. Body mass loss (a marker of hydration status) did not differ between trials (A: -0.9±0.8%, B: -0.7±0.5%, C: -0.4±0.4%, D: -0.3±0.5%; p=0.07) and (on average) was less than 2% in all trials (p≤0.009).
Conclusions: Ad libitum drinking during recommendation compliant work in the heat rarely resulted in dehydration.
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