Fig. 6. Ankle muscle root mean square electromyography. Subplots are soleus (Sol.; top), medial gastrocnemius (MG), lateral gastrocnemius (LG) and tibialis anterior (TA; bottom). In each subplot, bars are normalized mean stance phase root mean square (r.m.s.) average muscle activation of nine subjects. All r.m.s. values (unitless) are normalized to the unpowered 1.4 L^* condition. Error bars are ±1 s.e.m. Speeds/step lengths increase from left (0.8 L^*; 1.00 m s^–1) to right (1.4 L^*; 1.75 m s^–1) with unpowered walking (minutes 4–6) shown as white bars and powered walking (minutes 4–6) shown as gray bars. Numbers listed above bars indicate percentage difference in powered compared with unpowered condition. Asterisks indicate a statistically significant difference between powered and unpowered walking (P<0.05).