A fundamental feature of musculoskeletal design of the upper extremity is kinematic and muscle redundancy that has profound consequences for arm control in healthy people and individuals with spinal cord injury (SCI) at the cervical level (tetraplegia). After reviewing basic facts related to arm redundancy and associated complexities of arm motor control, our experimental data demonstrate that individuals with motor complete (n = 5) or incomplete (n = 1) SCI at C5-C7 can learn to perform a complex multi-joint task of tracking target forces by the arm. We conclude that individuals with SCI can benefit from musculoskeletal redundancy and alternative control strategies to accomplish complex multi-joint tasks.
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