Local loss of proprioception results in disruption of interjoint coordination during locomotion in the cat

To investigate the role of localized, proprioceptive feedback in the regula tion of interjoint coordination during locomotion, we substantially attenua ted neural feedback from the triceps surae muscles in one hindlimb in each of four cats using the method of self-reinnervation. After allowing the rec overy of motor innervation, the animals were filmed during level and ramp w alking. Deficits were small or undetectable during walking on the level sur face or up the ramp, behaviors that require a large range of forces in the triceps surae muscles. During walking down the ramp, when the triceps surae muscles normally undergo active lengthening, the ankle joint underwent a l arge yield and the coordination between ankle and knee was disrupted. The c orrelation of the deficit with the direction of length change and not muscl e force suggested that a loss of feedback from muscle spindle receptors was primarily responsible for the deficit. These results indicate an important role for the stretch reflex and stiffness regulation during locomotion.