Fig. 1.

Accessing spinal circuits involved in lower-limb motor control depends on the site of epidural stimulation. Electromyographic activity elicited by tonic stretch reflex in an individual with spinal spasticity during passive hip and knee flexion-extension movements (a) without stimulation and (b, c) during 50-Hz stimulation continuously applied from either of 2 stimulation sites (rostral and caudal active cathode sites, respectively) but otherwise unchanged stimulation parameters. Intensity was set at a submotor threshold level. Near complete suppression is achieved when shifting the stimulation site from low thoracic to upper lumbar spinal cord segments (cf. [7]). Shaded backgrounds mark flexion and extension phases of the passive movement in the supine position. Q = quadriceps; Add = adductors; Ham = hamstrings; TA = tibialis anterior; TS = triceps surae of the right (R) lower limb; subject 5 in [29] with chronic motor complete, sensory incomplete spinal cord injury (American Spinal Injury Association Impairment Scale grade B, neurological level of injury: C8)