Kenney W Larry, Zeman Michael J
Noll Physiological Research Center and the Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania 16802-6900, USA.
J Appl Physiol (1985). 2002 Jun;92(6):2256-63. doi: 10.1152/japplphysiol.01040.2001.
Critical environmental limits, defined as those above which heat balance cannot be maintained for a given metabolic heat production, have not been determined for unacclimated subjects. To characterize critical environmental limits and to derive evaporative heat exchange coefficients (K(e)') for unacclimated young men (n = 11) and women (n = 10), subjects of average aerobic fitness walked at 30% maximal aerobic capacity in an environmental chamber. Critical environmental conditions were defined as the psychrometric loci of dry-bulb temperature and water vapor pressure at which core (esophageal) temperature was forced out of equilibrium (heat gain exceeded heat loss). Compared with the men in our study, the women had significantly higher critical environmental limits (P < 0.001) in warm (34-38 degrees C), humid (>60%) environments, a function of their lower absolute metabolic heat production at the fixed relative exercise intensity. Isotherms constructed from biophysical models closely fit the data in this range of environments but underestimated empirically determined critical limits in hotter, drier environments. Sex-specific values of K(e)' were derived by partial calorimetry in the critical water vapor pressure environments, in which full skin wettedness occurred. There were no sex differences for K(e)' (men = 17.4, 15.5, and 14.2 W. m(-2). Torr(-1) and women = 16.8, 15.5, and 14.2 W. m(-2). Torr(-1) at 34, 36, and 38 degrees C, respectively). These K(e)' values were lower than those previously published for fully heat-acclimated men (18.4 W. m(-2). Torr(-1) at 36 degrees C) and women (17.7 W. m(-2). Torr(-1) at 36 degrees C and 15.5 W. m(-2). Torr(-1) at 38 degrees C) and may be used to model heat balance responses for unacclimated men and women working in hot environments.
临界环境极限是指在给定代谢产热情况下无法维持热平衡的环境条件，尚未针对未适应环境的受试者确定该极限。为了确定未适应环境的年轻男性（n = 11）和女性（n = 10）的临界环境极限并推导蒸发散热系数（K(e)'），平均有氧适能的受试者在环境舱中以最大有氧能力的30%进行步行。临界环境条件定义为干球温度和水汽压的湿度测定位点，此时核心（食管）温度被迫失衡（产热超过散热）。与我们研究中的男性相比，女性在温暖（34 - 38摄氏度）、潮湿（>60%）环境中的临界环境极限显著更高（P < 0.001），这是由于在固定相对运动强度下她们的绝对代谢产热较低。由生物物理模型构建的等温线在该环境范围内与数据拟合良好，但在更热、更干燥的环境中低估了经验确定的临界极限。在临界水汽压环境中通过部分量热法得出了K(e)'的性别特异性值，此时皮肤完全湿润。K(e)'没有性别差异（男性在34、36和38摄氏度时分别为17.4、15.5和14.2 W·m(-2)·Torr(-1)，女性分别为16.8、15.5和14.2 W·m(-2)·Torr(-1)）。这些K(e)'值低于先前公布的完全热适应男性（36摄氏度时为18.4 W·m(-2)·Torr(-1)）和女性（36摄氏度时为17.7 W·m(-2)·Torr(-1)，38摄氏度时为15.5 W·m(-2)·Torr(-1)）的值，可用于模拟未适应环境的男性和女性在炎热环境中的热平衡反应。
