Basic study on simultaneous stimulation to the antagonistic muscle pair by FES: force measurement at different muscle lengths

The simultaneous antagonistic stimulation method, which is to stimulate the antagonist with the agonist simultaneously, produces a good effect on the restoration of paralyzed motor function by FES, since it improves the steep response of electrically stimulated muscle. It was inferred in the previous study that the spinal cord reflex system contributed to the effect. For studying the response of neuromusculoskeletal system during the simultaneous stimulation in more detail, we measured the isometric force about the ankle joint fixed at different angles, i.e., at different muscle lengths, and evaluated the slope of force by piecewise linear approximation. It was observed that the effect of the simultaneous stimulation at position of ankle dorsi-flexion was different from the effect at the resting position and position of plantar flexion.