The soleus is the most commonly used muscle for H-reflex studies in humans, while limited
comparable data have been produced from the gastrocnemii muscles. This article reviews
the fundamental differences between the structure and function of the human soleus and
gastrocnemii muscles, including recent data published about their complex innervation
zones. Protocols for eliciting, recording, and assessing the H-reflex and M-wave magnitude
in the human triceps surae are also discussed.