Endpoint forces obtained during intraspinal microstimulation of the cat lumbar spinal cord - experimental and biomechanical model results

We studied the structure of endpoint forces produced by microstimulation of the cat spinal cord, and from combinations of muscles using a biomechanical model of the cat hindlimb. The forces evoked by microstimulation were of four types. At some stimulation sites, the force patterns exhibited a point of convergence where the active endpoint force was zero. The endpoint forces produced by activating combinations of muscles in the biomechanical model were of types similar to the experimental ones, although they demonstrated points of convergence in locations not observed experimentally. These results suggest that the spinal circuitry uses a subset of the possible muscular combinations.