A Biomechanical Analysis Of Rehabilitative Exercises For Subacromial Impingement Syndrome And/Or Rotator Cuff Tears

Abstract

Restrictions in range of motion (ROM) can occur due to subacromial impingement syndrome (SAIS) and rotator cuff tears (RCT). Alterations to scapular mobility reduces the subacromial space (SAS), compressing upon interposed tissues that reside within this area. This research examined muscle activity and co-activity among scapular stabilizer and rotator cuff musculature, and scapulothoracic kinematics. Thirty-two participants, sixteen male and sixteen female, completed two exercise sets; scapular stabilizer strengthening exercises (ScapSE) and body weight-bearing exercises (BWB). Exercises with low to moderate muscle activity of the rotator cuff (0-20%MVC, 20-40% MVC), higher scapular stabilizer activity, and advantageous co-activation (<80%) were recommended. ScapSE presented low to high activity in scapular stabilizer muscles, with Prone Shoulder Extension eliciting 11.9 ±10.6%MVC UT activity, and Y-Lifts eliciting 70 ±27.2%MVC. Moderate (21-40%MVC) scapular stabilizer muscle activity was expected throughout ScapSE; Serratus Anterior Strengthening, ranged from 21.4%MVC [UT] to 38.4%MVC [MT]. Lateral Flexion produced low SS activity of 3.1 ±2.2%MVC and IS activity of 14.2±8.1%MVC. Prone Shoulder Extension (UT/MT: 47%, UT/LT: 53%), Side Plank (39.0%, 39.7%, 41.1%), and Horizontal Abduction (UT/MT: 45%, UT/LT: 58%) presented advantageous co-activation. Exercises with ‘good’ to ‘excellent’ scapular muscle co-activity reduce UT hyperactivity, which may promote healthy upper limb kinematics. Exercises that presented with low to moderate muscle activity would be best suited in early-stage rehabilitation, while others with higher muscle activity may be better reserved for later-stage rehabilitation.