Cui Jian, Gao Zhaohui, Blaha Cheryl, Luck Jonathan Carter, Brandt Kristen, Sinoway Lawrence I
Penn State Health, Penn State Heart and Vascular Institute, Hershey, Pennsylvania.
Am J Physiol Regul Integr Comp Physiol. 2021 May 1;320(5):R757-R769. doi: 10.1152/ajpregu.00232.2020. Epub 2021 Mar 31.
Prior reports show that whole body heat stress attenuates the pressor response to exercise in young healthy subjects. The effects of moderate whole body heating (WBH; e.g., increase in internal temperature T of ∼0.4°C-0.5°C) or limb heating on sympathetic and cardiovascular responses to exercise in older healthy humans remain unclear. We examined the muscle sympathetic nerve activity (MSNA), mean arterial blood pressure (MAP), and heart rate (HR) in 14 older (62 ± 2 yr) healthy subjects during fatiguing isometric handgrip exercise and postexercise circulatory occlusion (PECO). The protocol was performed under normothermic, moderate WBH, and local limb (i.e., forearm) heating conditions during three visits. During the mild WBH stage (increase in T of <0.3°C), HR increased, whereas BP and MSNA decreased from baseline. Under the moderate WBH condition (increase in T of ∼0.4°C), BP decreased, HR increased, and MSNA was unchanged from baseline. Compared with the normothermic trial, the absolute MAP during fatiguing exercise and PECO was lower during the WBH trial. Moreover, MSNA and MAP responses (i.e., changes) to fatiguing exercise were also less than those seen during the normothermic trial. Limb heating induced a similar increase in forearm muscle temperature to that seen in the WBH trial (∼0.7°C-1.5°C). Limb heating did not alter resting MAP, HR, or MSNA. The MSNA and hemodynamic responses to exercise in the limb heating trial were not different from those in the normothermic trial. These data suggest that moderate WBH attenuates MSNA and BP responses to exercise in older healthy humans.
先前的报告表明，全身热应激会减弱年轻健康受试者对运动的升压反应。适度的全身加热（WBH；例如，体内温度T升高约0.4°C - 0.5°C）或肢体加热对老年健康人运动时交感神经和心血管反应的影响尚不清楚。我们在14名年龄较大（62±2岁）的健康受试者进行疲劳性等长握力运动和运动后循环闭塞（PECO）期间，检测了肌肉交感神经活动（MSNA）、平均动脉血压（MAP）和心率（HR）。该方案在三次就诊期间分别在常温、适度WBH和局部肢体（即前臂）加热条件下进行。在轻度WBH阶段（T升高<0.3°C），HR升高，而BP和MSNA较基线水平下降。在适度WBH条件下（T升高约0.4°C），BP下降，HR升高，MSNA与基线水平无变化。与常温试验相比，WBH试验期间疲劳运动和PECO期间的绝对MAP较低。此外，疲劳运动时MSNA和MAP的反应（即变化）也低于常温试验期间。肢体加热引起的前臂肌肉温度升高与WBH试验相似（约0.7°C - 1.5°C）。肢体加热未改变静息MAP、HR或MSNA。肢体加热试验中运动时的MSNA和血流动力学反应与常温试验无差异。这些数据表明，适度的WBH会减弱老年健康人运动时的MSNA和BP反应。
