Kinematics and muscle activation in subacromial pain syndrome patients and asymptomatic controls. (October 2021)

• Record Type: Journal Article
• Authors: Kolk, Arjen; Overbeek, Celeste L.; de Witte, Pieter Bas; Canete, Ana Navas; Reijnierse, Monique; Nagels, Jochem; Nelissen, Rob G.H.H.; de Groot, Jurriaan H.
• Is Part Of: Clinical biomechanics. Volume 89(2021)
• Publication Date: 2021-10
• Subjects: Rotator cuff -- Shoulder -- Co-contraction -- Kinematics -- Electromyography -- Shoulder impingement syndrome; Biomechanics -- Periodicals; Osteopathic medicine -- Periodicals; Biomechanics -- Periodicals; Osteopathic Medicine -- Periodicals; 612.76
• DOI: 10.1016/j.clinbiomech.2021.105483
• Languages: English
• ISSNs: 0268-0033

Abstract

Abstract: Background: Conflicting theories exist about the underlying cause of chronic subacromial pain in the middle-aged population. We aim to improve our understanding of kinematics and muscle activation in subacromial pain syndrome to provide insight in its pathophysiology. Methods: In a cross-sectional comparison of 40 patients with subacromial pain syndrome and 30 asymptomatic controls, three-dimensional shoulder kinematics and electromyography-based co-contraction in 10 shoulder muscles were independently recorded. Glenohumeral and scapulothoracic kinematics were evaluated during abduction and forward flexion. Co-contraction was expressed as an activation ratio, specifying the relative agonistic and antagonistic muscle activity in each muscle. Findings: During abduction and forward flexion, the contribution of glenohumeral motion to elevation and glenohumeral external rotation was lower in subacromial pain syndrome (at 120 0 abduction: −9°, 95% CI -14°- -3°; and − 8°, 95% CI -13°--3°, respectively), and was compensated by more scapulothoracic motion. The pectoralis major's activation ratio was significantly lower ( Z -score: -2.657, P = 0.008) and teres major's activation ratio significantly higher (Z-score: -4.088, P < 0.001) in patients with subacromial pain syndrome compared to the control group. Interpretation: Reduced glenohumeral elevation and external rotation in subacromial pain syndrome coincided with less teres major antagonistic activity during elevation. These biomechanical findings provide a scientific basis for intervention studies directed at stretching exercises to reduce glenohumeral stiffness in the treatment of subacromial pain syndrome, and teres major strengthening to improve humeral head depressor function. Highlights: Patients with Subacromial Pain Syndrome exhibit less glenohumeral elevation. Patients with Subacromial Pain Syndrome have less glenohumeral external rotation. Subacromial Pain Syndrome coincides with less antagonistic teres major activity.