Effectiveness of cervicothoracic junction manipulation versus placebo on shoulder muscle strength, electromyographic amplitude, and pain in participants with subacromial impingement syndrome
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Considerable research has demonstrated the effectiveness of rotator cuff strengthening and scapular stabilization training at improving pain and disability in patients with subacromial impingement syndrome (SAIS). Cervicothoracic junction (CTJ) manipulation has been shown to be effective for reducing shoulder pain and improving shoulder motions in patients with SAIS. However, the effects of CTJ manipulation on shoulder muscle strength and muscle activity have not been studied on this patient population. The purpose of this study was to examine the effectiveness of CTJ manipulation as compared to placebo in patients with SAIS on shoulder external rotation (ER) muscle strength during a maximal voluntary isometric contraction (MVIC), muscle activity of the middle deltoid (MDELT), supraspinatus (SUPR), and infraspinatus (INFR) muscles during MVIC of shoulder ER, and pain level. Thirty-two participants with SAIS were randomly assigned into two treatment groups: manipulation group ( n = 16) and placebo group (n = 16). Shoulder ER muscle strength was measured using hand-held dynamometry. Surface electromyographic (EMG) activity was recorded from the MDELT, SUPR, and INFR muscles during shoulder ER MVIC strength test. The Numeric Pain Rating Scale (NPRS) was used to assess shoulder pain level. All outcome measures (muscle strength, EMG activity, and pain level) were assessed at baseline, and immediately, 15 minutes, 30 minutes, 45 minutes, 48-72 hours, and 6-7 days after intervention. The results of this study showed no significant difference between groups over time in the shoulder ER strength, the EMG amplitude of the SUPR and INFR muscles and the NPRS (p > 0.05). However, a significant difference was found in the MDELT muscle between groups between 45 min and 48-72 hours after intervention, with the manipulation group having significantly increased muscle activity, coinciding with the placebo group having significantly reduced muscle activity. The results also showed that all participants had significant pain reduction over one week. Although CTJ manipulation reduced shoulder significantly, the CTJ manipulation did not result in changes of shoulder ER muscle strength and shoulder muscle activity.