Origin:  S1, sacral plexus, sciatic nerve, tibial nerve.

Recording Site:  Soleus

Reference Site:  Achilles tendon, just above the ankle

Ground:  Back of leg, halfway between the knee and recording site
 
Procedure:  The patient should be placed in the prone position (on stomach) with a pillow under their feet.  The recording electrode is placed over the soleus muscle, between the heads of the medial and lateral gastrocnemius muscles.  The reference electrode is placed above the back of the ankle over the Achilles tendon.  The stimulating site is at the center of the back of the knee, above the knee crease, in the fat pad area.  The polarity of the stimulator should be reversed.  Usually the H-reflex response is seen before the M-response and an interim of 5-10 seconds should occur in between stimulations to allow for repolarization of the nerve.