Soleus and Rectus Femoris Electromyography. a The mean soleus and rectus femoris EMG linear envelope from each walking condition is represented by the solid lines and +1 s.e.m. is represented by the dashed lines. b The mean soleus and rectus femoris r.m.s. of rectified EMG across the three walking conditions. All error bars represent ± 1 s.e.m.