Research Archive
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Load on the shoulder complex
The shoulder is a complex joint, but studies rarely focus on multi-site force analysis. A recent study by van Drongelen et al (2011) examined the shoulder by quantifying the forces and moments in all three joints of the shoulder complex (glenohumeral, acromioclavicular and sternoclavicular) during wheelchair propulsion and weight relief lifting in various populations.
Paraplegic subject as well as normals were tested with an instrumented wheelchair on a treadmill. A multi-axis load cell was used to measure forces and moments applied by the hand on the wheel rim. Kinematics were also recorded to obtain the orientation of the scapula , clavicle and other upper body segments. Variables analyzed include the net joint moments and joint reaction forces on the glenohumeral, acromio-clavicular and sternoclavicular joints.
Joint reaction forces in the glenohumeral joint were revealed to be 4 times larger than those in the other joints during weight relief lifting. Net moments were smaller in the glenohumeral joint compared to the others, due to external forces stabilizing this joint.
The authors conclude on the necessity of analyzing joint forces in the other joints in the shoulder complex in order to identify possible techniques of reducing shoulder pain.