Crandall C G, Stephens D P, Johnson J M
Institute for Exercise and Environmental Medicine, Presbyterian Hospital, Dallas, TX 75231, USA.
Med Sci Sports Exerc. 1998 Apr;30(4):490-6. doi: 10.1097/00005768-199804000-00004.
Isometric handgrip exercise in hyperthermia has been shown to reduce cutaneous vascular conductance (CVC) by inhibiting the cutaneous active vasodilator system.
To identify whether this response was initiated by muscle metaboreceptors, in seven subjects two 3-min bouts of isometric handgrip exercise in hyperthermia were performed, followed by 2 min of postexercise ischemia (PEI). An index of forearm skin blood flow (laser-Doppler flowmetry) was measured on the contralateral arm at an unblocked site and at a site at which adrenergic vasoconstrictor function was blocked via bretylium iontophoresis to reveal active cutaneous vasodilator function unambiguously. Sweat rate was measured via capacitance hygrometry, CVC was indexed from the ratio of skin blood flow to mean arterial pressure and was expressed as a percentage of maximal CVC at that site. In normothermia, neither isometric exercise nor PEI affected CVC (P > 0.05).
The first bout of isometric handgrip exercise in hyperthermia reduced CVC at control sites and this reduction persisted through PEI (pre-exercise: 59.8 +/- 5.4, exercise: 49.8 +/- 4.9, PEI: 49.7 +/- 5.3% of maximum; both P < 0.05), whereas there were no significant changes in CVC at the bretylium treated sites. The succeeding bout of isometric exercise in hyperthermia significantly reduced CVC at both untreated (pre-exercise: 59.0 +/- 4.8, exercise: 47.3 +/- 4.0, PEI: 50.1 +/- 4.1% of maximum; both P < 0.05) and bretylium treated sites (pre-exercise: 61.4 +/- 7.3, exercise: 50.6 +/- 5.1, PEI: 53.9 +/- 6.0% of maximum, both P < 0.05). At both sites, CVC during PEI was lower than during the pre-exercise period (P < 0.05). Sweat rate rose significantly during both bouts of isometric exercise and remained elevated during PEI.
These data suggest that the reduction in CVC during isometric exercise in hyperthermia, including the inhibition of the active vasodilator system, is primarily mediated by muscle metaboreceptors, whereas central command or muscle mechanoreceptors have less influence.
研究表明，热环境下的等长握力运动可通过抑制皮肤活性血管舒张系统来降低皮肤血管传导性（CVC）。
为确定这种反应是否由肌肉代谢感受器引发，对7名受试者进行了热环境下的两次3分钟等长握力运动，随后进行2分钟的运动后缺血（PEI）。通过激光多普勒血流仪测量对侧手臂未阻滞部位和经溴苄铵离子电渗疗法阻滞肾上腺素能血管收缩功能部位的前臂皮肤血流指数，以明确揭示活性皮肤血管舒张功能。通过电容湿度测定法测量出汗率，CVC通过皮肤血流与平均动脉压的比值来计算，并表示为该部位最大CVC的百分比。在常温下，等长运动和PEI均未影响CVC（P>0.05）。
热环境下的第一次等长握力运动降低了对照部位的CVC，且这种降低在PEI期间持续存在（运动前：最大CVC的59.8±5.4%，运动时：49.8±4.9%，PEI时：49.7±5.3%；P均<0.05），而溴苄铵处理部位的CVC无显著变化。热环境下随后的等长运动回合显著降低了未处理部位（运动前：最大CVC的59.0±4.8%，运动时：47.3±4.0%，PEI时：50.1±4.1%；P均<0.05）和溴苄铵处理部位（运动前：61.4±7.3%，运动时：50.6±5.1%，PEI时：53.9±6.0%；P均<0.05）的CVC。在两个部位，PEI期间的CVC均低于运动前（P<0.05）。两次等长运动期间出汗率均显著升高，并在PEI期间保持升高。
这些数据表明，热环境下等长运动期间CVC的降低，包括对活性血管舒张系统的抑制，主要由肌肉代谢感受器介导，而中枢指令或肌肉机械感受器的影响较小。
