Recent studies have reported positive outcomes following use of the Tibion Bionic Leg (TBL). Here we investigated EMG changes during overground walking while wearing the TBL. In healthy participants, EMG modulation was reduced and EMG phasing was altered in proximal muscles while EMG amplitude was altered in distal muscles. Responses to the TBL in persons post-stroke were more subtle, but reveal EMG reorganization towards normal. Thus, functional improvements may result from repetitive practice with more appropriate EMG phasing and increased activation.