Department of Nutrition, Exercise and Sports, Section for Integrative Physiology, University of Copenhagen, Copenhagen, Denmark.
FAME Laboratory, Department of Exercise Science, University of Thessaly, Karies, Trikala, Greece.
PLoS One. 2018 Oct 24;13(10):e0205321. doi: 10.1371/journal.pone.0205321. eCollection 2018.
To evaluate the prevalence of dehydration in occupational settings and contextualize findings to effects on performance in cognitively dominated tasks, simple and complex motor tasks during moderate and high heat stress.
The study included an occupational part with hydration assessed in five industries across Europe with urine samples collected from 139 workers and analyzed for urine specific gravity. In addition, laboratory experiments included eight male participants completing mild-intensity exercise once with full fluid replacement to maintain euhydration, and once with restricted water intake until the dehydration level corresponded to 2% bodyweight deficit. Following familiarization, euhydration and dehydration sessions were completed on separate days in random order (cross-over design) with assessment of simple motor (target pinch), complex motor (visuo-motor tracking), cognitive (math addition) and combined motor-cognitive (math and pinch) performance at baseline, at 1°C (MOD) and 2°C (HYPER) delta increase in body core temperature.
The field studies revealed that 70% of all workers had urine specific gravity values ≥1.020 corresponding to the urine specific gravity (1.020±0.001) at the end of the laboratory dehydration session. At this hydration level, HYPER was associated with reductions in simple motor task performance by 4±1%, math task by 4±1%, math and pinch by 9±3% and visuo-motor tracking by 16±4% (all P<0.05 compared to baseline), whereas no significant changes were observed when the heat stress was MOD (P>0.05). In the euhydration session, HYPER reduced complex (tracking) motor performance by 10±3% and simple pinch by 3±1% (both P<0.05, compared to baseline), while performance in the two cognitively dominated tasks were unaffected when dehydration was prevented (P>0.05).
Dehydration at levels commonly observed across a range of occupational settings with environmental heat stress aggravates the impact of hyperthermia on performance in tasks relying on combinations of cognitive function and motor response accuracy.
评估职业环境中脱水的发生率，并将在中度和高度热应激下认知主导任务、简单和复杂运动任务中脱水对表现的影响进行背景化分析。
该研究包括职业部分，在欧洲五个行业评估了 139 名工人的水分摄入情况，并收集尿液样本进行尿比重分析。此外，实验室实验包括 8 名男性参与者，他们在轻度运动时进行了一次充分液体补充以保持水平衡，以及一次限制水摄入，直到脱水水平对应于体重损失 2%。在熟悉之后，在随机顺序（交叉设计）中分别在不同日子进行水平衡和脱水状态下的评估，在基线、1°C（MOD）和 2°C（HYPER）核心体温升高 1°C 时进行简单运动（目标夹捏）、复杂运动（视觉运动跟踪）、认知（数学加法）和结合运动认知（数学和夹捏）的表现评估。
现场研究显示，70%的工人尿比重值≥1.020，相当于实验室脱水状态结束时的尿比重（1.020±0.001）。在这种水分水平下，HYPER 与简单运动任务表现降低 4±1%、数学任务降低 4±1%、数学和夹捏任务降低 9±3%和视觉运动跟踪任务降低 16±4%相关（与基线相比，所有均 P<0.05），而当热应激为 MOD 时未观察到显著变化（P>0.05）。在水平衡状态下，HYPER 降低了复杂（跟踪）运动表现 10±3%和简单夹捏表现 3±1%（均 P<0.05，与基线相比），而当脱水被预防时，认知主导任务的表现不受影响（P>0.05）。
在各种职业环境中常见的水平下脱水，加上环境热应激，会加剧高温对依赖认知功能和运动反应准确性的任务表现的影响。
