Motor control retraining exercises for shoulder impingement: effects on function, muscle activation, and biomechanics in young adults

Abstract

Objective: Evidence for effective management of shoulder impingement is limited. The present study aimed to quantify the clinical, neurophysiological, and biomechanical effects of a scapular motor control retraining for young individuals with shoulder impingement signs.

Method: Sixteen adults with shoulder impingement signs (mean age 22 ± 1.6 years) underwent the intervention and 16 healthy participants (24.8 ± 3.1years) provided reference data. Shoulder function and pain were assessed using the Shoulder Pain and Disability Index (SPADI) and other questionnaires. Electromyography (EMG) and 3-dimensional motion analysis was used to record muscle activation and kinematic data during arm elevation to 90° and lowering in 3 planes. Patients were assessed pre and post a 10-week motor control based intervention, utilizing scapular orientation retraining.

Results: Pre-intervention, patients reported pain and reduced function compared to the healthy participants (SPADI in patients 20 ± 9.2; healthy 0 ± 0). Post-intervention, the SPADI scores reduced significantly (P < .001) by a mean of 10 points (±4). EMG showed delayed onset and early termination of serratus anterior and lower trapezius muscle activity pre-intervention, which improved significantly post-intervention (P < .05). Pre-intervention, patients exhibited on average 4.6-7.4° less posterior tilt, which was significantly lower in 2 arm elevation planes (P < .05) than healthy participants. Post-intervention, upward rotation and posterior tilt increased significantly (P < .05) during 2 arm movements, approaching the healthy values.

Conclusion: A 10-week motor control intervention for shoulder impingement increased function and reduced pain. Recovery mechanisms were indicated by changes in muscle recruitment and scapular kinematics. The efficacy of the intervention requires further examined in a randomized control trial.

Figure 1

Acromion marker cluster location (AMC) and electromyography electrode placements.

Figure 2

Muscle activation timing in relation to arm position: (a) serratus anterior muscle activation onset during the elevation phase and termination during the lowering phase in the frontal plane. (b) lower trapezius onset and termination during arm movement in the sagittal plane. Mean and standard deviation (error bar) arm position of muscle onset and termination of muscle activity. Graph to show electromyography muscle activation relative to arm elevation angle in one participant prior to (c) and post- (d) the ten week intervention

Figure 3

Scapular kinematics: (a) mean upward rotation from rest to 90° arm elevation (b) mean upward rotation from 90° arm elevation to rest (c) posterior tilt during sagittal plane arm movement from rest to 90° (d) posterior tilt during sagittal plane arm movement from 90° to rest.