Three-dimensional shoulder kinematics during a pressure relief technique and wheelchair transfer.
OBJECTIVE
To assess 3-dimensional scapulothoracic and glenohumeral kinematics in able-bodied subjects during a weight-relief raise and while transferring to and from a wheelchair.


METHODS
Repeated-measures analysis of variance.


METHODS
Research laboratory.


METHODS
Twenty-five able-bodied subjects without spinal cord injury or shoulder symptoms (20 men, 5 women; age range, 20-37y).


METHODS
Completion of weight-relief raise and transfer tasks.


METHODS
An electromagnetic motion capture system tracked 3-dimensional position and orientation of the thorax, scapula, and humerus. Absolute angular values assessed included scapular downward and upward rotation, internal and external rotation, and posterior and anterior tipping all relative to the thorax, as well as humeral internal and external rotation relative to the scapula. Data were compared across 3 phases of the weight-relief raise and for transfer direction (leading arm, trailing arm).


RESULTS
Key findings included significantly increased anterior tipping and internal rotation of the scapula and decreased scapular upward rotation and external rotation of the humerus during the weight-relief raise. The leading arm showed significantly greater scapular anterior tipping and internal rotation and less scapular upward rotation and humeral external rotation than the trailing arm during the final phase of the transfer.


CONCLUSIONS
Both the weight-relief raise and transfer result in scapular and humeral positions and directions of motion that may negatively impact the available subacromial space. This may present increased risk for injury or progression of shoulder pain in persons who must routinely perform these tasks.
D000328:Adult; D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D055590:Electromagnetic Phenomena; D005260:Female; D006801:Humans; D006811:Humerus / Q000502:physiology; D008297:Male; D009068:Movement / Q000502:physiology*; D011312:Pressure; D012399:Rotation; D012540:Scapula / Q000502:physiology; D012785:Shoulder Joint / Q000502:physiology*; D016474:Weight-Bearing / Q000502:physiology*; D014910:Wheelchairs