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首页> 外文期刊>Journal of Neurophysiology >Muscle length and joint angle influence spinal but not corticospinal excitability to the biceps brachii across forearm postures
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Muscle length and joint angle influence spinal but not corticospinal excitability to the biceps brachii across forearm postures

机译：肌肉长度和关节角度影响脊髓，但不会穿过前臂姿势的二头肌Brachii的皮质兴奋性

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摘要

Forearm rotation (supination/pronation) alters corticospinal excitability to the biceps brachii, but it is unclear whether corticospinal excitability is influenced by joint angle. muscle length, or both. Thus the purpose of this study was to separately examine elbow joint angle and muscle length on corticospinal excitability. Corticospinal excitability to the biceps and triceps brachii was measured using motor evoked potentials (MEPs) elicited via transcranial magnetic stimulation. Spinal excitability was measured using cervicomedullary motor evoked potentials (CMEPs) elicited via transmastoid electrical stimulation. Elbow angles were manipulated with a fixed biceps brachii muscle length (and vice versa) across five unique postures: 1) forearm neutral, elbow flexion 90 degrees; 2) forearm supinated, elbow flexion 90 degrees; 3) forearm pronated, elbow flexion 90 degrees; 4) forearm supinated, elbow flexion 78 degrees; and 5) forearm pronated, elbow flexion 113 degrees. A musculoskeletal model determined biceps brachii muscle length for postures 1-3, and elbow joint angles (postures 4-5) were selected to maintain biceps length across forearm orientations. MEPs and CMEPs were elicited at rest and during an isometric contraction of 10% of maximal biceps muscle activity. At rest, MEP amplitudes to the biceps were largest during supination, which was independent of elbow joint angle. CMEP amplitudes were not different when the elbow was fixed at 90 degrees but were largest in pronation when muscle length was controlled. During an isometric contraction, there were no significant differences across forearm postures for either MEP or CMEP amplitudes. These results highlight that elbow joint angle and biceps brachii muscle length can each independently influence spinal excitability.
机译：前臂旋转（苏旋解/翻）改变了与二头肌的动力激发成二头肌，但目前尚不清楚有皮质激发性是否受关节角度影响。肌肉长度，或两者。因此，本研究的目的是分别检查肘关节角度和肌肉长度对皮质源性兴奋性。使用经过经颅磁刺激引发的电动机诱发电位（MEP）测量与二头肌和三头肌毛刺的皮质兴奋性。使用通过变速器电刺激引发的宫颈髓质型电动机诱发电位（CMEP）测量脊柱兴奋性。用固定的二头肌Brachii肌肉长度（反之亦然）操纵肘部角度，横跨五个独特的姿势：1）前臂中性，肘部屈曲90度; 2）前臂纯合，肘部屈曲90度; 3）牙齿上的弯头屈曲90度; 4）前臂纯合，肘部屈曲78度; 5）前臂伸展，肘部屈曲113度。肌肉骨骼模型确定了姿势1-3的二头肌肌肉长度，选择肘关节角（姿势4-5），以在前臂取向上保持二头肌长度。在休息和等距收缩期间诱导MEPS和CMEPs，占最大二头肌肌肉活动的10％。在静止时，吡脂的MEP振幅最大，其在弯管期间是完全的弯头关节角度。当弯头固定在90度时，CMEP振幅与但是当肌肉长度被控制在90度时，肌肉长度最大的肌肉长度。在等距收缩期间，Forearm姿势对于MEP或CMEP幅度的前臂姿势没有显着差异。这些结果突出显示弯头关节角度和二头肌肌肉长度可以各自独立地影响脊柱兴奋性。

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