Wright Beatty Heather E, Hardcastle Stephen G, Boulay Pierre, Flouris Andreas D, Kenny Glen P
a Human and Environmental Physiology Research Unit, School of Human Kinetics University of Ottawa , Ottawa , Canada.
J Occup Environ Hyg. 2015;12(9):625-34. doi: 10.1080/15459624.2015.1029613.
Older adults have been reported to have a lower evaporative heat loss capacity than younger adults during exercise when full sweat evaporation is permitted. However, it is unclear how conditions of restricted evaporative and convective heat loss (i.e., high humidity, clothing insulation) alter heat stress. to the purpose of this study was to examine the heat stress responses of young and older males during and following exercise in a warm/humid environment under two different levels of air velocity. Ten young (YOUNG: 24±2 yr) and 10 older (OLDER: 59±3 yr) males, matched for body surface area performed 4×15-min cycling bouts (15-min rest) at a fixed rate of heat production (400 W) in warm/humid conditions (35°C, 60% relative humidity) under 0.5 (Low) and 3.0 (High) m·s(-1) air velocity while wearing work coveralls. Rectal (Tre) and mean skin (MTsk) temperatures, heart rate (HR), local sweat rate, % max skin blood flow (SkBF) (recovery only), and blood pressure (recovery only) were measured. High air velocity reduced core and skin temperatures (p < 0.05) equally in YOUNG and OLDER males (p > 0.05) but was more effective in reducing cardiovascular strain (absolute and % max HR; p < 0.05) in YOUNG males (p < 0.05). Greater increases in local dry heat loss responses (% max SkBF and cutaneous vascular conductance) were detected across time in OLDER than YOUNG males in both conditions (p < 0.05). Local dry heat loss responses and cardiovascular strain were attenuated during the High condition in YOUNG compared to OLDER (p < 0.05). High air velocity reduced the number of males surpassing the 38.0°C Tre threshold from 90% (Low) to 50% (High). Despite age-related local heat loss differences, YOUNG and OLDER males had similar levels of heat stress during intermittent exercise in warm and humid conditions while wearing work coveralls. Increased air velocity was effective in reducing heat stress equally, and cardiovascular strain to a greater extent, in YOUNG and OLDER males, and may be useful for mitigating heat stress in all workers.
据报道，在允许完全汗液蒸发的运动过程中，老年人的蒸发散热能力低于年轻人。然而，尚不清楚蒸发和对流散热受限的条件（即高湿度、衣物隔热）如何改变热应激。本研究的目的是在两种不同风速水平下，研究年轻男性和老年男性在温暖/潮湿环境中运动期间及运动后的热应激反应。十名年轻男性（YOUNG：24±2岁）和十名老年男性（OLDER：59±3岁），根据体表面积进行匹配，在温暖/潮湿条件（35°C，相对湿度60%）下，以固定产热率（400W）进行4组15分钟的骑行运动（每组运动后休息15分钟），风速分别为0.5（低）和3.0（高）m·s-1，同时穿着工作服。测量直肠温度（Tre）、平均皮肤温度（MTsk）、心率（HR）、局部出汗率、最大皮肤血流量百分比（SkBF）（仅在恢复阶段测量）和血压（仅在恢复阶段测量）。高风速使年轻男性和老年男性的核心温度和皮肤温度同等降低（p<0.05），但在降低年轻男性的心血管应激（绝对心率和最大心率百分比；p<0.05）方面更有效（p<0.05）。在两种条件下，随着时间推移，老年男性的局部干热损失反应（最大SkBF百分比和皮肤血管传导率）的增加幅度均大于年轻男性（p<0.05）。与老年男性相比，年轻男性在高风速条件下的局部干热损失反应和心血管应激有所减弱（p<0.05）。高风速使超过38.0°C Tre阈值的男性人数从90%（低风速）降至50%（高风速）。尽管存在与年龄相关的局部热损失差异，但年轻男性和老年男性在穿着工作服于温暖潮湿环境中进行间歇运动时，热应激水平相似。增加风速在年轻男性和老年男性中均能有效同等程度地降低热应激，并在更大程度上降低心血管应激，可能有助于减轻所有劳动者的热应激。
