San Diego State University, San Diego, CA, USA (School of Exercise and Nutritional Sciences).
Int J Occup Med Environ Health. 2023 May 23;36(2):192-200. doi: 10.13075/ijomeh.1896.02065. Epub 2023 May 17.
Following heat illness, a return to activity may require passing a heat tolerance test (HTT). However, there are several logistical limitations to the widespread use of the HTT. Thus, it would be advantageous to develop a test that could be conducted in a thermoneutral (~22°C) environment to predict heat tolerance status. The purpose of the current study was to determine the sensitivity and specificity of using the criteria of a heart rate (HR) ≥130 bpm following 30 min of thermoneutral exercise in detecting heat-intolerant and heat-tolerant individuals.
Sixty-five subjects visited the lab on 3 separate days. The first visit consisted of completing a maximal oxygen uptake (VO2 max) test to assess cardiovascular fitness. For lab visits 2 and 3, subjects randomly completed a 2-hour walking treadmill test in either a hot (40°C, 40% relative humidity [RH]) or thermoneutral (22°C, 40% RH) environment.
Forty-eight subjects were classified as heat-intolerant and 17 subjects as heat-tolerant. Using the criterion of a HR ≥130 bpm at 30 min of exercise in the thermoneutral environment, specificity (54%) and sensitivity (100%) of passing the HTT was calculated. Secondary analysis using multiple regression revealed 3 significant variables for predicting ending HR during the HTT. They were: 1) absolute VO2 max (l/min), 2) age, and 3) HR at 30 min of exercise during thermoneutral exercise.
Exercise in a thermoneutral environment had a positive predictive value of 100%, thus, if a subject has a HR ≥130 bpm at 30 min of exercise in a thermoneutral environment, they are very likely to fail a subsequent 2-hour HTT in the heat and be classified as heat-intolerant. Therefore, prior screening has the potential to save time and money, along with providing safety to a heat-intolerant subject. Int J Occup Med Environ Health. 2023;36(2):192-200.
热疾病后，恢复活动可能需要通过耐热能力测试（HTT）。然而，HTT 的广泛使用存在一些后勤限制。因此，开发一种可以在热中性（~22°C）环境中进行的测试来预测耐热能力状态将是有利的。本研究的目的是确定在 30 分钟热中性运动后心率（HR）≥130 bpm 的标准用于检测耐热不良和耐热个体的敏感性和特异性。
65 名受试者在 3 天内分别访问实验室。第一次访问包括进行最大摄氧量（VO2 max）测试，以评估心血管健康状况。对于实验室访问 2 和 3，受试者随机在热（40°C，40%相对湿度[RH]）或热中性（22°C，40%RH）环境中完成 2 小时步行跑步机测试。
48 名受试者被归类为耐热不良，17 名受试者被归类为耐热。在热中性环境下运动 30 分钟时 HR≥130 bpm 的标准下，通过 HTT 的特异性（54%）和敏感性（100%）。使用多元回归进行的二次分析显示，有 3 个预测 HTT 期间结束 HR 的重要变量。它们是：1）绝对 VO2 max（升/分钟），2）年龄，3）热中性运动 30 分钟时的 HR。
热中性环境下的运动具有 100%的阳性预测值，因此，如果受试者在热中性环境下运动 30 分钟时 HR≥130 bpm，则他们很可能在随后的 2 小时 HTT 中失败，并且被归类为耐热不良。因此，预先筛查有可能节省时间和金钱，同时为耐热不良的受试者提供安全性。国际职业医学与环境卫生杂志。2023；36（2）：192-200。
