Human and Environmental Physiology Research Unit, University of Ottawa, Ottawa, CANADA.
Med Sci Sports Exerc. 2020 Oct;52(10):2242-2249. doi: 10.1249/MSS.0000000000002373.
Increasing age is associated with decrements in sweat rate that compromise whole-body total heat loss (evaporative + dry heat exchange) in both men and women during moderate-to-vigorous exercise in dry heat. Similarly, young women also display reductions in sweating (that lower evaporative heat loss) relative to young men in such conditions. Nevertheless, it remained unclear whether these effects act synergistically to exacerbate the age-related decline in whole-body total heat loss in women relative to men. We therefore assessed the interrelation between age and sex on whole-body total heat loss during light, moderate, and vigorous exercise in dry heat.
To achieve this, we used direct and indirect calorimetry to assess whole-body total heat loss and metabolic heat production (respectively) in 46 men and 34 women age between 18 and 70 yr. Participants performed three, 30-min bouts of cycling at metabolic heat productions of 150 (light), 200 (moderate), and 250 (vigorous) W·m, each separated by 15-min recovery in dry heat (40°C, ~15% relative humidity).
Whole-body total heat loss was 5% lower in women relative to men during moderate and vigorous exercise (both, P < 0.01), irrespective of age. Total heat loss declined with age during moderate and vigorous exercise in both men and women (all, P < 0.050), although the rate of that decline (4% per decade) was similar between men and women across all exercise bouts (all, P > 0.050).
We show that, when assessed in dry heat, whole-body total heat loss is lower in women relative to men, irrespective of age. Furthermore, total heat loss declines with increasing age in both men and women during moderate-to-vigorous exercise, albeit the rate of that decline is not appreciably modified by sex.
在干燥热环境中进行中等至剧烈运动时，年龄的增长与男女的出汗率下降有关，这会降低全身总热损失（蒸发+干热交换）。同样，在这种情况下，年轻女性的出汗量（降低蒸发散热损失）也相对年轻男性减少。然而，目前尚不清楚这些影响是否协同作用，导致女性相对于男性的全身总热损失随年龄增长而加剧。因此，我们评估了年龄和性别对干燥热环境中轻、中、剧烈运动时全身总热损失的相互关系。
为了实现这一目标，我们使用直接和间接测热法分别评估了 46 名男性和 34 名年龄在 18 至 70 岁之间的女性在轻、中、剧烈运动时的全身总热损失和代谢产热量。参与者在干燥热环境（40°C，相对湿度约 15%）中进行了三次，每次 30 分钟的自行车骑行，每个 30 分钟骑行之间间隔 15 分钟的恢复期，代谢产热量分别为 150（轻度）、200（中度）和 250（剧烈）W·m。
在中等和剧烈运动时，女性的全身总热损失比男性低约 5%（均 P < 0.01），与年龄无关。在中等和剧烈运动时，男性和女性的总热损失随年龄增长而下降（均 P < 0.050），但在所有运动阶段，男女之间的下降率（每十年约 4%）相似（均 P > 0.050）。
我们表明，在干燥热环境中评估时，无论年龄大小，女性的全身总热损失均低于男性。此外，在中等至剧烈运动时，男性和女性的总热损失随年龄增长而下降，尽管性别对下降率的影响不大。
