Mulla Daanish M, McDonald Alison C, Keir Peter J
Occupational Biomechanics Laboratory, Department of Kinesiology, McMaster University, Hamilton, ON L8S 4K1, Canada.
Occupational Biomechanics Laboratory, Department of Kinesiology, McMaster University, Hamilton, ON L8S 4K1, Canada.
Hum Mov Sci. 2018 Jun;59:121-133. doi: 10.1016/j.humov.2018.04.001. Epub 2018 Apr 11.
The rotator cuff muscles are prominent stabilizers of the shoulder and are vulnerable to muscle fatigue. Rotator cuff fatigue may result in subacromial impingement (SAI) through the superior translation of the humeral head. Scapular changes have been reported inconsistently, but may prevent SAI. The purpose of this study was to quantify changes in scapular kinematics, as well as muscle activity during glenohumeral motions following targeted rotator cuff fatigue. Ten healthy men completed four planar glenohumeral motions (cross-flexion, frontal, scapular, and sagittal plane elevation) prior to and immediately following a rotator cuff fatigue protocol on two separate days. Scapular kinematics and muscle activity of thirteen muscles were recorded. Scapular protraction decreased significantly with fatigue during scapular plane elevation (p < 0.001; η = 0.74). Although not significant, large effect sizes were found with decreased scapular protraction during elevation in the frontal (p = 0.012; η = 0.52) and sagittal planes (p = 0.007; η = 0.58), as well as decreased scapular medial rotation during cross-flexion (p = 0.008; η = 0.56). Between-subject variability (standard deviations from 2.3° to 14.5°) and within-subject day-to-day differences (upwards of 10° deviation in the opposite direction) were high among all kinematic changes following fatigue. Considerable day-to-day differences in scapular stabilizer muscle activity in response to fatigue were present. Due to the degrees of freedom at the upper extremity, individuals can employ a variety of compensatory strategies to fatigue. The variable compensatory strategies across the scapular stabilizers resulted in individual-specific scapular kinematic changes that could act as either impingement-sparing or impingement-promoting. The high variance in day-to-day differences within-subjects indicates that kinematic and muscular responses to fatigue may be adaptive within individuals over time.
肩袖肌群是肩部重要的稳定肌，且易出现肌肉疲劳。肩袖疲劳可能通过肱骨头向上移位导致肩峰下撞击（SAI）。关于肩胛变化的报道并不一致，但肩胛变化可能会预防SAI。本研究的目的是量化在针对性肩袖疲劳后，盂肱关节运动期间肩胛运动学以及肌肉活动的变化。10名健康男性在两个不同日期，于肩袖疲劳方案实施之前和之后立即完成了四种平面盂肱关节运动（交叉屈曲、额状面、肩胛面和矢状面抬高）。记录了13块肌肉的肩胛运动学和肌肉活动情况。在肩胛面抬高过程中，随着疲劳的出现，肩胛前伸显著减少（p < 0.001；η = 0.74）。虽然不显著，但在额状面（p = 0.012；η = 0.52）和矢状面（p = 0.007；η = 0.58）抬高时，肩胛前伸减少以及在交叉屈曲时肩胛内旋减少（p = 0.008；η = 0.56）均发现了较大的效应量。在疲劳后的所有运动学变化中，个体间变异性（标准差为2.3°至14.5°）和个体内每日差异（相反方向偏差超过10°）都很高。针对疲劳，肩胛稳定肌的肌肉活动存在相当大的每日差异。由于上肢的自由度，个体可以采用多种代偿策略来应对疲劳。肩胛稳定肌的多种代偿策略导致了个体特异性的肩胛运动学变化，这些变化可能起到预防撞击或促进撞击的作用。个体内每日差异的高变异性表明，随着时间推移，个体对疲劳的运动学和肌肉反应可能具有适应性。
