A new technique is being used to monitor at the unit level the primary afferent neural activity entering the spinal cord during normal walking. Approximately 10 fine wires are implanted in the L7 and S1 dorsal root ganglia (DRG) of a cat. After recovery from surgery, each wire usually records separable unit activity from 1-3 DRG cells, and each unit is typically stable for 1-4 days. This permits correlation of unit activity with kinesiological records of normal and perturbed gait as well as accurate characterization of receptor modality under anesthesia. 67 units covering the entire range of unmyelinated and myelinated afferents have been so studied and characterized to date. Preliminary results indicate some previously unpredicted activity patterns which will require further study. Neural and electromyographic activity is being correlated with records of muscle force and joint angle from chronically implanted strain and length gauges developed for this project. In particular, the forces and EMG output of individual muscles of triceps surae have been studied during walking, running, and jumping in implanted cats.