Fluid balance during hot-dry and warm-humid heat stress while adhering to occupational hydration recommendations.
Xiujing Zhao, Cory L Butts, Zachary J McKenna et al.
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In 30 seconds
This randomized controlled trial assessed fluid balance in 20 healthy adults during moderate-intensity work in hot-dry (HD) and warm-humid (WH) environments while following NIOSH hydration recommendations. Results showed that while body mass loss remained below 2%, hydration efficiency and net fluid balance were significantly better in WH compared to HD, suggesting the fixed-volume hydration strategy may be excessive in certain conditions.
Key findings
- Whole-body sweat rate was greater in HD than WH (0.53 ± 0.13 vs 0.35 ± 0.10 L/h, P < 0.001).
- Body mass gain was higher in WH compared to HD (1.1 ± 0.5% vs 0.6 ± 0.4%, P < 0.001).
- Net fluid balance was significantly greater in WH (0.70 ± 0.27 L vs 0.40 ± 0.26 L, P < 0.001).
- Hydration efficiency was better in WH (48.9 ± 19.3% vs 28.2 ± 18.0%, P < 0.001).
Why it matters
Understanding fluid balance in varying environmental conditions is crucial for preventing heat-related illnesses in workers. This study highlights the need for tailored hydration strategies that consider environmental factors rather than a one-size-fits-all approach.