Fig. 5. Rectified electromyographic (EMG) signals (after 7 Hz high-pass filter) versus time [normal walking, walking with the aiding horizontal force (AHF) and impeding horizontal force (IHF) devices, respectively] for the soleus (SOL), medial gastrocnemius (MGAS) and lateral gastrocnemius (LGAS) muscles for a representative subject. Vertical lines indicate heel strikes and toe-off for the right leg. Black horizontal bars indicate the burst analyzed during stance (between 0–60%). The bar graphs on the right depict mean muscle activity (± s.e.m.) during stance for all subjects while walking normally (white), walking with the AHF (grey), and walking with the IHF (black). The asterisk denotes a significant difference in mean muscle activity compared to normal walking (all P values <0.012).