Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada.
Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba, Japan.
Exp Physiol. 2021 Feb;106(2):450-462. doi: 10.1113/EP089025. Epub 2020 Dec 28.
What is the central question of this study? Does short-term heat acclimation enhance whole-body evaporative heat loss and augment nitric oxide synthase (NOS)-dependent cutaneous vasodilatation and NOS- and cyclooxygenase (COX)-dependent sweating, in exercising older men? What is the main finding and its importance? Our preliminary data (n = 8) demonstrated that short-term heat acclimation improved whole-body evaporative heat loss, but it did not influence the effects of NOS and/or COX inhibition on cutaneous vasodilatation or sweating in older men during an exercise-heat stress. These outcomes might imply that although short-term heat acclimation enhances heat dissipation in older men, it does not modulate NOS- and COX-dependent control of cutaneous vasodilatation or sweating on the forearm.
Ageing is associated with decrements in whole-body heat loss (evaporative + dry heat exchange), which might stem from alterations in nitric oxide synthase (NOS)- and cyclooxygenase (COX)-dependent cutaneous vasodilatation and sweating. We evaluated whether short-term heat acclimation would (i) enhance whole-body heat loss primarily by increasing evaporative heat loss, and (ii) augment NOS-dependent cutaneous vasodilatation and NOS- and COX-dependent sweating, in exercising older men. Eight older men [mean (SD) age, 59 (8) years] completed a calorimetry and microdialysis trial before and after 7 days of exercise-heat acclimation. For the calorimetry trials, whole-body evaporative and dry heat exchange were assessed using direct calorimetry during 30 min bouts of cycling at light, moderate and vigorous metabolic heat productions (150, 200 and 250 W/m , respectively) in dry heat (40°C, 20% relative humidity). For the microdialysis trials, local cutaneous vascular conductance and sweat rate were assessed during 60 min exercise in the heat (35°C, 20% relative humidity) at four dorsal forearm skin sites treated with lactated Ringer solution (control), NOS inhibitor, COX inhibitor or combined NOS and COX inhibitors, via microdialysis. Evaporative heat loss during moderate (P = 0.036) and vigorous (P = 0.021) exercise increased after acclimation. Inhibition of NOS alone reduced cutaneous vascular conductance to a similar extent before and after acclimation (P < 0.040), whereas separate and combined NOS and COX inhibition had no significant effects on sweating relative to the control site (P = 0.745). Our preliminary results might suggest that short-term heat acclimation improves evaporative heat loss, but does not significantly modulate the contributions of NOS or COX to cutaneous vasodilatation or sweating on the forearm in older men during an exercise-heat stress.
本研究的核心问题是什么？短期热适应是否会增强全身蒸发散热，并增强一氧化氮合酶（NOS）依赖性皮肤血管舒张以及 NOS 和环氧化酶（COX）依赖性出汗，在老年男性进行运动时？主要发现及其重要性是什么？我们的初步数据（n=8）表明，短期热适应可改善全身蒸发散热，但不会影响 NOS 和/或 COX 抑制对老年男性在运动-热应激期间皮肤血管舒张或出汗的影响。这些结果可能意味着，尽管短期热适应可增强老年男性的散热能力，但不会调节 NOS 和 COX 依赖性控制前臂皮肤血管舒张或出汗。
衰老与全身热损失（蒸发+干热交换）的减少有关，这可能源于一氧化氮合酶（NOS）和环氧化酶（COX）依赖性皮肤血管舒张和出汗的改变。我们评估了短期热适应是否会（i）主要通过增加蒸发散热来增强全身热损失，以及（ii）增强运动时老年男性的 NOS 依赖性皮肤血管舒张和 NOS 和 COX 依赖性出汗。八名老年男性[平均（SD）年龄，59（8）岁]在 7 天的运动-热适应后完成了热量测定和微透析试验。在热量测定试验中，通过在 40°C，20%相对湿度的干热环境中以 150、200 和 250 W/m 2 的代谢产热分别进行 30 分钟的自行车运动，使用直接热量法评估全身蒸发和干热交换。在微透析试验中，在四个背部前臂皮肤部位通过微透析用乳酸盐林格溶液（对照），NOS 抑制剂，COX 抑制剂或 NOS 和 COX 抑制剂联合处理，在 35°C，20%相对湿度的热环境中进行 60 分钟的运动，评估局部皮肤血管导纳和出汗率。适应后，中等强度（P=0.036）和剧烈运动（P=0.021）时的蒸发散热增加。单独抑制 NOS 会降低适应前后的皮肤血管导纳（P<0.040），而 NOS 和 COX 单独和联合抑制对与对照部位相比出汗没有显著影响（P=0.745）。我们的初步结果可能表明，短期热适应可改善蒸发散热，但不会显著调节 NOS 或 COX 对前臂皮肤血管舒张或出汗的贡献，在老年男性进行运动-热应激时。
