Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, CANADA.
FAME Laboratory, Department of Exercise Science, University of Thessaly, Volos, GREECE.
Med Sci Sports Exerc. 2021 Oct 1;53(10):2196-2206. doi: 10.1249/MSS.0000000000002698.
To mitigate rises in core temperature >1°C, the American Conference of Governmental Industrial Hygienists (ACGIH) recommends upper limits for heat stress (action limit values [ALV]), defined by wet-bulb globe temperature (WBGT) and a worker's metabolic rate. However, these limits are based on data from young men and are assumed to be suitable for all workers, irrespective of age or health status. We therefore explored the effect of aging, type 2 diabetes (T2D), and hypertension (HTN) on tolerance to prolonged, moderate-intensity work above and below these limits.
Core temperature and heart rate were assessed in healthy, heat unacclimatized young (18-30 yr, n = 13) and older (50-70 yr) men (n = 14) and heat unacclimatized older men with T2D (n = 10) or HTN (n = 13) during moderate-intensity (metabolic rate: 200 W·m-2) walking for 180 min (or until termination) in environments above (28°C and 32°C WBGT) and below (16°C and 24°C WBGT) the ALV for continuous work at this intensity (25°C WBGT).
Work tolerance in the 32°C WBGT was shorter in men with T2D (median [IQR]; 109 [91-173] min; P = 0.041) and HTN (120 [65-170] min; P = 0.010) compared with healthy older men (180 [133-180] min). However, aging, T2D, and HTN did not significantly influence (i) core temperature or heart rate reserve, irrespective of WBGT; (ii) the probability that core temperature exceeded recommended limits (>1°C) under the ALV; and (iii) work duration before core temperature exceeded recommended limits (>1°C) above the ALV.
These findings demonstrate that T2D and HTN attenuate tolerance to uncompensable heat stress (32°C WBGT); however, these chronic diseases do not significantly impact thermal and cardiovascular strain, or the validity of ACIGH recommendations during moderate-intensity work.
为了将核心体温升高超过 1°C 控制在最低水平，美国政府工业卫生学家会议（ACGIH）提出了热应激的上限值（行动限值，ALV），这是通过湿球黑球温度（WBGT）和工人代谢率来定义的。然而，这些限值是基于年轻人的数据，假设适用于所有工人，无论其年龄或健康状况如何。因此，我们探讨了衰老、2 型糖尿病（T2D）和高血压（HTN）对超过和低于这些限值的长时间、中等强度工作的耐受能力的影响。
在未适应热环境的年轻（18-30 岁，n=13）和老年（50-70 岁，n=14）男性以及未适应热环境的老年男性（T2D 组 n=10，HTN 组 n=13）中，评估了核心体温和心率，他们在环境温度分别为（28°C 和 32°C 的 WBGT）和低于（16°C 和 24°C 的 WBGT）ALV 的情况下，以 200 W·m-2 的代谢率进行了 180 分钟（或直至终止）的中等强度（25°C WBGT）行走。
在 32°C WBGT 环境下，T2D（中位数[IQR]；109 [91-173] 分钟；P=0.041）和 HTN（120 [65-170] 分钟；P=0.010）患者的工作耐受性明显短于健康老年男性（180 [133-180] 分钟）。然而，无论 WBGT 如何，衰老、T2D 和 HTN 并没有显著影响（i）核心体温或心率储备；（ii）在 ALV 下核心体温超过推荐限值（>1°C）的概率；以及（iii）在 ALV 以上核心体温超过推荐限值（>1°C）之前的工作时间。
这些发现表明，T2D 和 HTN 降低了对无法补偿的热应激（32°C WBGT）的耐受性；然而，这些慢性疾病并没有显著影响中等强度工作期间的热应激和心血管应激，也没有影响 ACIGH 建议的有效性。
