This repeated-measures study tested how erect versus slouched thoracic posture affects the shoulder in 34 healthy adults. Using a 3D digitizer, it measured scapular kinematics, active abduction ROM, and isometric abduction force in the scapular plane. The goal was to quantify the long-assumed link between spinal alignment and shoulder function.
When a patient with shoulder pain slumps, the scapula loses upward rotation and posterior tilt during elevation, closing down the subacromial space. This paper converts the old clinical teaching that "posture affects the shoulder" into measured numbers: 23.6° less abduction and 16.2% less force at shoulder height in slouch.
The force loss is position-specific. It appears at 90° but not with the arm down, which fits a length-tension mechanism as the deltoid and supraspinatus shorten with anterior scapular tilt. Clinically, this is why assessing and correcting thoracic posture belongs in the workup of impingement, not just glenohumeral or rotator cuff exam.
Keep the limits in mind: these are healthy young subjects tested at extreme end-range postures under static conditions, so the magnitudes may overstate everyday activity.
This repeated-measures study tested how erect versus slouched thoracic posture affects the shoulder in 34 healthy adults. Using a 3D digitizer, it measured scapular kinematics, active abduction ROM, and isometric abduction force in the scapular plane. The goal was to quantify the long-assumed link between spinal alignment and shoulder function.
When a patient with shoulder pain slumps, the scapula loses upward rotation and posterior tilt during elevation, closing down the subacromial space. This paper converts the old clinical teaching that "posture affects the shoulder" into measured numbers: 23.6° less abduction and 16.2% less force at shoulder height in slouch.
The force loss is position-specific. It appears at 90° but not with the arm down, which fits a length-tension mechanism as the deltoid and supraspinatus shorten with anterior scapular tilt. Clinically, this is why assessing and correcting thoracic posture belongs in the workup of impingement, not just glenohumeral or rotator cuff exam.
Keep the limits in mind: these are healthy young subjects tested at extreme end-range postures under static conditions, so the magnitudes may overstate everyday activity.