Objective: To determine the kinematics and kinetics of performing a weight-relief maneuver in persons with C5 and C6 quadriplegia.
Study design: A three-dimensional kinematic and kinetic analysis was performed on the upward phase of a weight-relief maneuver with the use of a motion analysis system, two force platforms, and an instrumented seat. Electromyography (EMG) data were collected from the upper pectoralis, anterior deltoid, latissimus dorsi, and biceps brachii muscles of the right upper limb.
Setting: Biomechanics laboratory.
Subjects: Seven persons with C5 and C6 quadriplegia (ASIA A and B) with "flickers" (grade 1/5) or less in wrist flexor and triceps brachii muscles.
Main outcome measures: Angular displacements and associated moments of the shoulder, elbow, and wrist, kinematic variables describing the position and displacement of the trunk and upper limbs, and EMG data.
Results: Subjects lifted from a forward flexed posture with their arms adducted against their trunks. During the course of lifting, they flexed their shoulders and wrists and extended their elbows. They generated peak mean (+/- SE) shoulder and elbow flexor moments of .65 (+/-.04) and .41 (+/-.06) N x m x kg(-1), respectively. Shoulder adductor moments increased over the course of the lift. The median (and interquartile range) mean EMG activity in the upper pectoralis and the anterior deltoid muscles were 63% (35%-76%) and 44% (36%-49%) of EMG obtained during maximal voluntary contractions, respectively.
Conclusion: Persons with quadriplegia with paralysis of the triceps brachii muscles lift themselves by generating active shoulder flexor and adductor moments. They also rely on wrist flexor moments that are generated by the stretch of the wrist flexor muscles.