M408 School of Sports Science, Exercise and Health, The University of Western Australia, 35 Stirling Hwy, Crawley, WA, 6009, Australia,
Eur J Appl Physiol. 2014 Apr;114(4):859-65. doi: 10.1007/s00421-013-2817-2. Epub 2014 Jan 8.
Shear stress is a known stimulus to vascular adaptation in humans. However, it is not known whether thermoregulatory reflex increases in blood flow and shear can induce conduit artery adaptation.
Ten healthy young volunteers therefore underwent 8 weeks of 3 × weekly bouts of 30 min lower limb heating (40 °C) during which the upper body was not directly heated. Throughout each leg heating session, a pneumatic cuff was placed on one forearm and inflated to unilaterally restrict reflex-mediated blood flow responses.
Each bout of leg heating significantly increased brachial artery shear rate in the uncuffed arm (96 ± 97 vs 401 ± 96 l/s, P < 0.01), whereas no change was apparent in the cuffed arm (83 ± 69 vs 131 ± 76 l/s, P = 0.67). Repeated episodic exposure to leg heating enhanced brachial artery endothelial function (measured by flow-mediated dilation) in the uncuffed arm from week 0 (5.2 ± 1.9 %) to week 4 (7.7 ± 2.6 %, P < 0.05), before returning to baseline levels by week 8. No adaptation was evident in the cuffed arm.
We conclude that repeated increases in core temperature, induced via lower limb heating, resulted in upper limb conduit artery vascular adaptation which was dependent upon increases in shear stress. To our knowledge this is the first study to establish a beneficial systemic impact of thermoregulatory reflexes on conduit artery function in humans.
切应力是已知的血管适应人类的刺激。然而，目前尚不清楚热调节反射增加血流量和切应力是否可以诱导导管动脉适应。
因此，10 名健康的年轻志愿者接受了 8 周的 3 次每周 30 分钟的下肢加热（40°C），在此期间，上半身未直接加热。在每次腿部加热过程中，将一个气动袖带放在一只前臂上并充气，以单侧限制反射介导的血流反应。
每次腿部加热都会显著增加未充气臂的肱动脉剪切率（96 ± 97 对 401 ± 96 l/s，P < 0.01），而充气臂没有明显变化（83 ± 69 对 131 ± 76 l/s，P = 0.67）。反复间歇性下肢加热增强了未充气臂的肱动脉内皮功能（通过血流介导的扩张来测量），从第 0 周（5.2 ± 1.9%）到第 4 周（7.7 ± 2.6%，P < 0.05），然后在第 8 周恢复到基线水平。在充气臂中没有观察到适应。
我们得出结论，通过下肢加热反复增加核心体温导致上肢导管血管适应，这依赖于剪切应力的增加。据我们所知，这是第一项在人类中建立热调节反射对导管动脉功能有益的系统影响的研究。
