Changes in circulatory dynamics of upper extremity and saccadic reaction time during neck flexion

本研究调查了上肢肌肉循环动力学在维持颈部屈曲任务和颈部屈曲任务伴随眼动反应任务期间的变化。颈部屈曲角度随机设定为0°、10°和20°。在这两项任务中，研究人员都测量了肱二头肌和肱三头肌的肌肉氧合、肌肉上的皮肤血流量、心电图、血压和心输出量。此外，在颈部屈曲时，腓神经记录肌肉交感神经活动（MSNA）。在屈曲过程中，肌肉氧合随屈曲角度的增加而显著增加。与单纯的屈伸颈任务相比，在屈伸颈与眼动反应任务中，肌肉的氧化作用更大。在20°屈曲时，任务之间存在显著差异。此外，在联合任务下，肱二头肌的皮肤血流量往往比单独的颈部屈曲任务要小。在20°屈曲时，任务之间存在显著差异。在心电图、血压或心输出量方面没有发现明显的任务效应。保持颈部屈曲时，上肢肌肉内的血流量明显增加。当屈曲颈部任务与眼动反应任务同时进行时，血流量增加更多。颈部屈曲时，MSNA有降低的趋势。这表明与维持颈部屈曲相关的大脑激活影响延髓内控制循环反应的血管舒缩中枢，导致肌肉血管舒张。此外，在颈部屈曲和眼动联合反应任务中，额外的大脑激活似乎提供了协同效应，皮肤血管收缩导致的皮肤血流量减少可能与增加的血流量以及肌肉血管扩张有关。

The present study investigated changes in circulatory dynamics of upper extremity muscles during a task involving maintaining neck flexion and during the neck flexion task accompanied with an eye movement reaction task. Neck flexion angles were randomly set at 0°, 10° and 20°. Muscle oxygenation in the biceps brachii and triceps brachii, skin blood flow over the muscles, electrocardiograms, blood pressure and cardiac output were measured during both tasks. Furthermore, muscle sympathetic nerve activity (MSNA) was recorded from peroneal nerve during the neck flexion. During the neck flexion task, oxygenation in muscles increased significantly with angle of neck flexion. Oxygenation in muscles tended to be larger in the neck flexion task with the eye movement reaction task than in the neck flexion task alone. A significant difference between tasks was found at 20° flexion. Furthermore, skin blood flow over the biceps brachii tended to be smaller under the combined task than under the neck flexion task alone. A significant difference between tasks was found at 20° flexion. No significant task effects were found in electrocardiograms, blood pressure or cardiac output. Blood flow within upper extremity muscles was clearly increased while maintaining neck flexion. Blood flow increased more when the neck-flexion task accompanied the eye movement reaction task. MSNA was tendency to decrease during neck flexion. This suggests that brain activation associated with maintaining neck flexion influences the vasomotor center in the medulla oblongata controlling circulatory responses, leading to vasodilatation in muscles. Furthermore, additional brain activation appears to offer synergistic effects during the combined neck flexion and eye movement reaction tasks, and reduction of skin blood flow by skin vasoconstriction might be related to increased blood flow in addition to vasodilatation in muscles.