上斜方肌肌筋膜激痛點在過肩運動員於執行提肩疲勞任務後對肩胛骨動作及肩胛肌肉活性的影響：橫斷性研究

Abstract

背景：過肩型運動項目中，反覆執行大幅且高速的上肢過肩動作可能會造成運動員的肌肉過度負荷及產生疲勞。具有肩關節症狀的過肩運動員被證實存在有肩胛骨動作及肩胛肌肉活性改變的現象，尤其上斜方肌過度活化可能造成肌肉疲勞且產生肌筋膜肌痛點。過去文獻探討了各式肌肉疲勞所造成的改變，但上斜方肌疲勞以及上斜方肌具有肌筋膜激痛點所造成的影響，目前仍尚未被探討。實驗目的：本次實驗有兩個目的：（1）比較存在與不存在上斜方肌肌筋膜肌痛點之過肩運動員，在執行肩胛平面手臂上抬動作時肩胛動作與肩胛肌肉活性的差異。（2）比較存在與不存在上斜方肌肌筋膜肌痛點之過肩運動員，經提肩疲勞任務後，執行肩胛平面手臂上抬動作之肩胛動作與肩胛肌肉活性的影響及差異。實驗設計：本實驗招募業餘過肩運動員，並根據上斜方肌是否存在肌筋膜肌痛點分為兩組。提肩疲勞任務中，受試者需使用最大力量維持提肩胛動作，直到力量減少超過一半並且持續五秒以上即停止。本實驗在疲勞任務執行前、後，使用三維電磁動作分析儀和肌電圖紀錄肩胛平面手臂上抬之肩胛骨動作與肩胛肌肉活性。量測項目：肩胛骨動作（上/下轉、外/內轉及後/前傾角度）以及經表面肌電圖收集之肩胛肌肉活性（上斜方肌、下斜方肌、前鋸肌、上斜方肌/下斜方肌比值、上斜方肌/前鋸肌比值）為本實驗之結果測量項目。結果：肩胛平面手臂上抬之肩胛骨動作與肩胛肌肉活性在兩組之間無顯著差異，僅下斜方肌在具有肌筋膜肌痛點組別中具有較高的肌肉活性。完成疲勞任務後相較於執行任務前，上斜方肌（離心收縮期）與下斜方肌活性較高，且上斜方肌／下斜方肌比值較低，但兩組之間無顯著差異。結論：本次實驗結果不支持上斜方肌肌筋膜肌痛點與肩胛骨動作缺損的發生有直接關聯性，即使在肌肉疲勞後，也不支持其關係性。而上斜方肌肌筋膜肌痛點造成該肌肉功能缺損時，下斜方肌可能為主要代償肩胛骨上轉動作的肌肉。

Background: The repetitive overhead movements with wide range of motion and high velocity are required in overhead sports activity. It may give rise to shoulder region muscles overloading and fatigue. Altered scapular kinematics and muscle activities was found in overhead athletes with shoulder pathology, especially the overactivity of upper trapezius (UT) muscle which might cause muscle fatigue and myofascial trigger point (MTrP). Numerous studies have investigated the effects of shoulder muscle fatigue. However, the effects of UT hosting MTrP and UT muscle fatigue is still unknown. Objective: The purposes of the study were to (1) compare the scapular kinematics and muscle activities during arm elevation in overhead athletes with and without UT MTrPs; (2) compare the effects of scapula elevation fatigue task on the scapular kinematics and muscle activities during arm elevation in overhead athletes with and without UT MTrPs. Design: Participants with UT MTrP and without UT MTrP were recruited in this study. Each patient preformed a scapular elevation fatigue task until they could not maintain over a half of peak force for 5 seconds. Three-dimensional electromagnetic motion analysis system and electromyography muscle activity were used to record scapular kinematics and muscle activation during scapular plane arm elevation before and after the fatigue task. Main outcome measure: Scapular kinematics (upward/downward rotation, external/internal rotation, posterior/anterior tilt) and muscle activity (upper trapezius, lower trapezius, serratus anterior, and UT/LT, UT/ SA) were the outcomes of the study. Results: There was no group difference in scapular kinematics and muscle activities during scapular plane arm elevation, except for higher activity of LT in MTrP group. In comparisons of pre- and post-fatigue condition, increased activity of UT (eccentric phase) and LT, as well as decreased UT/LT ratio were found after fatigue protocol without group difference. Conclusion: Based on our results, it does not support that the presence of UT MTrP is related to the scapular kinematics impairment during arm elevation in overhead athletes even after muscle fatigue task. The lower trapezius muscle may be the main compensatory scapular upward rotator when the UT dysfunction occurs due to the presence of MTrP.