Heat acclimation increases skin vasodilation and sweating but not cardiac baroreflex responses in heat-stressed humans.
Heat acclimation increases skin vasodilation and sweating but not cardiac baroreflex responses in heat-stressed humans.
复制标题
DOI：
10.1152/japplphysiol.00063.2003
复制
发表时间：
2003-10
影响因子：
3.3
通讯作者：
F. Yamazaki;K. Hamasaki
中科院分区：
文献类型：
--
作者：
F. Yamazaki;K. Hamasaki
在本研究中，为了验证运动热适应通过改善心脏压力反射控制来提高直立耐力的假设，我们检查了心脏压力反射和温度调节反应，包括皮肤血管扩张和出汗反应，在为期6天的运动-热适应计划前后的全身加热期间[4次20分钟的50%运动在高温（36 ℃; 50%相对湿度）下静置10分钟后的氧摄取峰值速率]。10名健康的年轻志愿者参加了这项研究。在热适应程序之前和之后的测试日，受试者在仰卧位休息45 min和75 °头高位倾斜（HUT）6 min期间接受全身热应激。心跳动脉压和HR。HUT在预适应测试中在7名受试者中诱导晕厥前体征，在后适应测试中在6名受试者中诱导晕厥前体征，并且倾斜时间在驯化前（241 +/- 33 s）和驯化后（283 +/- 24 s）测试之间没有显著差异。热习服没有改变HR食管温度（Tes）关系和心脏压力反射敏感性在加热过程中的斜率。热习服降低了前臂和手背皮肤血管舒张反应的Tes阈值，降低了前臂和胸部出汗反应的Tes阈值（P < 0.05）。这些结果表明，短期热习服不改变自发的压力感受性反射控制的HR在热应激期间，虽然它诱导的适应性变化的散热反应在nonglabrous皮肤。
In the present study, to test the hypothesis that exercise-heat acclimation increases orthostatic tolerance via the improvement of cardiac baroreflex control in heated humans, we examined cardiac baroreflex and thermoregulatory responses, including cutaneous vasomotor and sudomotor responses, during whole body heating before and after a 6-day exercise-heat acclimation program [4 bouts of 20-min exercise at 50% peak rate of oxygen uptake separated by 10-min rest in the heat (36 degrees C; 50% relative humidity)]. Ten healthy young volunteers participated in the study. On the test days before and after the heat acclimation program, subjects underwent whole body heat stress produced by a hot water-perfused suit during supine rest for 45 min and 75 degrees head-up tilt (HUT) for 6 min. The sensitivity of the arterial baroreflex control of heart rate (HR) was calculated from the spontaneous changes in beat-to-beat arterial pressure and HR. The HUT induced a presyncopal sign in seven subjects in the preacclimation test and in six subjects in the postacclimation test, and the tilting time did not differ significantly between the pre- (241 +/- 33 s) and postacclimation (283 +/- 24 s) tests. Heat acclimation did not change the slope in the HR-esophageal temperature (Tes) relation and the cardiac baroreflex sensitivity during heating. Heat acclimation decreased (P < 0.05) the Tes thresholds for cutaneous vasodilation in the forearm and dorsal hand and for sweating in the forearm and chest. These findings suggest that short-term heat acclimation does not alter the spontaneous baroreflex control of HR during heat stress, although it induces adaptive change of the heat dissipation response in nonglabrous skin.