As pioneers in muscle (EMG) and force biofeedback, we helped to define the predictors of improved arm use or ambulation. EMG biofeedback involves conditioning muscle responses so that spastic muscles are trained to become less active and weak, antagonist muscles are recruited first in isolation and then during functional activities. Operant conditioning of spinal stretch reflexes elicited by sudden movements about a specific joint allow for the recording of EMG evoked reflex responses and the subsequent “shaping” or down-training of hyperactive responses among patients with stroke.