General Procedures.

We compared muscle synergies in 12 intact adult Sprague–Dawley rats, 9 adult rats spinalized at spinal segment T9/10 as neonates (∼P5–P6), and 9 adult complete SCI rats derived from the 12 intact rats. All procedures were in accordance with US Department of Agriculture and Institutional Animal Care and Use Committee (IACUC) guidelines and had Drexel IACUC approval. For intact and neonatal SCI animals, EMG electrodes and a pelvis orthosis were implanted to attach a robot for subsequent rehabilitation and locomotor testing (59). Spinal transection followed after 2–4 wk in intact rats. Full technical details are given in SI Appendix.