Using neural stimulation techniques, we have quantified voluntary activation and corticomotor excitability of surgically transferred muscle in individuals with quadriplegia resulting from SCI. We are using the Simtk forum to share the data we collected. Our publications should be referenced for detailed information regarding our objectives, subjects, methods, and results. Here, we provide a summary of our work.

We found that maximum voluntary activation (percentage of the motorneuron pool that can be voluntarily recruited during maximum effort) is more complete in individuals with quadriplegia who have undergone biceps-to-triceps transfer relative to those who have undergone posterior deltoid-to-triceps transfer. Both the biceps-to-triceps and the posterior deltoid-to-triceps transfers are surgical procedures that enable active elbow extension via reassignment of a nonparalyzed donor muscle (biceps or deltoid) to the insertion of the paralyzed triceps. The greater voluntary activation after biceps transfer we found in functionally relevant postures augmented the greater force generating capacity of the biceps muscle, leading to increased post-surgery elbow extension strength relative to when the posterior deltoid is transferred. In another study, using transcranial magnetic stimulation to non-invasively stimulate the motor cortex, we found that posture-dependent excitability of the corticomotor pathway to the biceps is altered following SCI and surgical transfer relative to the nonimpaired biceps. Thus, if initial training of the transferred biceps is facilitated in postures that correspond to greatest corticomotor excitability, training postures cannot be based on the excitability of the nonimpaired biceps.