Charkoudian Nisha, Mitchell Katherine M, Yurkevicius Beau R, Luippold Adam J, Bradbury Karleigh E, Kenefick Robert W
United States Army Research Institute of Environmental Medicine, Natick, Massachusetts.
Am J Physiol Regul Integr Comp Physiol. 2019 Oct 1;317(4):R571-R575. doi: 10.1152/ajpregu.00143.2019. Epub 2019 Jul 31.
Exposure to hot environments augments cutaneous vasodilation and sweating during exercise compared with these responses in cooler environments. The effects of hypobaric hypoxia on these responses are less clear, as are the effects of heat and simulated altitude combined. We evaluated the individual and potential additive effects of environmental heat and hypobaric hypoxia on skin blood flow and sweating responses during exercise. Thirteen volunteers (11 M, 2 F; age 25.3 ± 6.1 yr; height 177 ± 9 cm; weight 81.2 ± 16.8 kg) completed 30 min of steady-state (SS) exercise on a cycle ergometer at 50% V̇o during four separate conditions: ) sea level thermoneutral (SLTN; 250 m, 20°C, 30-50% RH), ) sea level hot (SLH; 250 m, 35°C, 30% RH), ) simulated altitude thermoneutral (ATN; 3,000 m, 20°C, 30-50% RH), and ) simulated altitude hot (AH; 3,000 m, 35°C, 30% RH). Skin blood flow and local sweating rate (LSR) were recorded on the ventral forearm. During exercise, SS cutaneous vascular conductance in AH (63 ± 31% peak) and SLH (52 ± 19% peak) were significantly higher than both SLTN (20 ± 9% peak, < 0.001) and ATN (25 ± 12% peak, < 0.05) but were not different from each other ( > 0.05). SS LSR was similarly increased in the hot environments but unaffected by simulated altitude. We propose that multiple antagonistic mechanisms during exposure to 3,000-m simulated altitude result in no net effect on skin blood flow or sweating responses during exercise in thermoneutral or hot environments.
与在较凉爽环境中的反应相比，暴露于热环境会增强运动期间的皮肤血管舒张和出汗。低压缺氧对这些反应的影响尚不清楚，热和模拟海拔相结合的影响也不明确。我们评估了环境热和低压缺氧对运动期间皮肤血流量和出汗反应的个体及潜在相加作用。13名志愿者（11名男性，2名女性；年龄25.3±6.1岁；身高177±9厘米；体重81.2±16.8千克）在四种不同条件下，于功率自行车上以50%最大摄氧量完成30分钟的稳态（SS）运动：）海平面热中性（SLTN；250米，20°C，30 - 50%相对湿度），）海平面热（SLH；250米，35°C，30%相对湿度），）模拟海拔热中性（ATN；3000米，20°C，30 - 50%相对湿度），以及）模拟海拔热（AH；3000米，35°C，30%相对湿度）。在前臂腹侧记录皮肤血流量和局部出汗率（LSR）。运动期间，AH组（63±31%峰值）和SLH组（52±19%峰值）的SS皮肤血管传导率显著高于SLTN组（20±9%峰值，P<0.001）和ATN组（25±12%峰值，P<0.05），但彼此之间无差异（P>0.05）。热环境中SS LSR同样增加，但不受模拟海拔影响。我们提出，在暴露于3000米模拟海拔期间，多种拮抗机制导致在热中性或热环境中运动时对皮肤血流量或出汗反应无净影响。
