Havenith G, Coenen J M, Kistemaker L, Kenney W L
TNO Human Factors Research Institute, Soesterberg, The Netherlands.
Eur J Appl Physiol Occup Physiol. 1998 Feb;77(3):231-41. doi: 10.1007/s004210050327.
Multiple heterogeneous groups of subjects (both sexes and a wide range of maximal oxygen uptake VO2max, body mass, body surface area (AD),% body fat, and AD/mass coefficient) exercised on a cycle ergometer at a relative (%VO2max, REL) or an absolute (60 W) exercise intensity in a cool (CO 21 degrees C, 50% relative humidity), warm humid (WH 35 degrees C, 80%) and a hot dry (HD 45 degrees C, 20%) environment. Rectal temperature (Tre) responses were analysed for the influence of the individual's characteristics, environment and exercise intensity. Exposures consisted of 30-min rest, followed by 60-min exercise. The Tre was negatively correlated with mass in all conditions. Body mass acted as a passive heat sink in all the conditions tested. While negatively correlated with VO2max and VO2max per kilogram body mass in most climates, Tre was positively correlated with VO2max and VO2max per kilogram body mass in the WH/REL condition. Thus, when evaporative heat loss was limited as in WH, the higher heat production of the fitter subjects in the REL trials determined Tre and not the greater efficiency for heat loss associated with high VO2max. Body fatness significantly affected Tre only in the CO condition, where, with low skin blood flows (measured as increases in forearm blood flow), the insulative effect of fat was pronounced. In the warmer environments, high skin blood flows offset the resistance offered by peripheral adipose tissue. Contrary to other studies, Tre was positively correlated with AD/mass coefficient for all conditions tested. For both exercise types used, being big (a high heat loss area and heat capacity) was apparently more beneficial from a heat strain standpoint than having a favourable AD/mass coefficient (high in small subjects). The total amount of variance in Tre responses which could be attributed to individual characteristics was dependent on the climate and the type of exercise. Though substantial for absolute exercise intensities (52%-58%) the variance explained in Tre differed markedly for relative intensities: 72% for the WH climate with its limited evaporative capacity, and only 10%-26% for the HD and CO climates. The results showed that individual characteristics play a significant role in determining the responses of body core temperature in all conditions tested, but their contribution was low for relative exercise intensities when evaporative heat loss was not restricted. This study demonstrated that effects of individual characteristics on human responses to heat stress cannot be interpreted without taking into consideration both the heat transfer properties of the environment and the metabolic heat production resulting from the exercise type and intensity chosen. Their impact varies substantially among conditions.
多组异质性受试者（包括不同性别、具有广泛的最大摄氧量VO₂max、体重、体表面积（AD）、体脂百分比以及AD/体重系数）在冷环境（CO 21摄氏度，相对湿度50%）、温暖潮湿环境（WH 35摄氏度，80%）和炎热干燥环境（HD 45摄氏度，20%）中，以相对强度（%VO₂max，REL）或绝对强度（60瓦）在功率自行车上进行运动。分析直肠温度（Tre）反应，以研究个体特征、环境和运动强度的影响。暴露包括30分钟的休息，随后是60分钟的运动。在所有条件下，Tre与体重呈负相关。在所有测试条件下，体重都起到了被动散热的作用。虽然在大多数气候条件下，Tre与VO₂max以及每千克体重的VO₂max呈负相关，但在WH/REL条件下，Tre与VO₂max以及每千克体重的VO₂max呈正相关。因此，当如在WH环境中蒸发散热受限，在REL试验中身体状况较好的受试者较高的产热决定了Tre，而不是与高VO₂max相关的更大散热效率。体脂仅在CO条件下对Tre有显著影响，在该条件下，皮肤血流较低（以前臂血流增加来衡量），脂肪的隔热作用明显。在较温暖的环境中，高皮肤血流抵消了外周脂肪组织提供的阻力。与其他研究相反，在所有测试条件下，Tre与AD/体重系数呈正相关。对于所使用的两种运动类型，从热应激的角度来看，体型较大（散热面积大且热容量大）显然比具有良好的AD/体重系数（小个子受试者该系数高）更有益。Tre反应中可归因于个体特征的总方差量取决于气候和运动类型。对于绝对运动强度，这一比例较大（52%-58%），但对于相对强度，Tre中所解释的方差在不同气候条件下差异显著：在蒸发能力有限的WH气候中为72%，而在HD和CO气候中仅为10%-26%。结果表明，在所有测试条件下，个体特征在决定体核温度反应中起着重要作用，但在蒸发散热不受限制的相对运动强度下，其贡献较低。这项研究表明，在不考虑环境的热传递特性以及所选运动类型和强度所产生的代谢产热的情况下，无法解释个体特征对人体热应激反应的影响。它们的影响在不同条件下有很大差异。
