SPINAL WITHDRAWAL REFLEXES IN THE HUMAN LOWER LIMBS

Abstract

An analysis of spinal skin reflexes in lower limbs of healthy subjects was made in hopes that the pattern might aid in interpreting the abnormal responses associated with upper motor neuron disease. Noxious stimuli were applied to various regions of the lower limb and electromyographic recordings of reflex responses studied in the gluteus maximus, vastus medialis, gastrocnemius and tibialis anterior muscles. Reflex patterns were found to vary according to the area of ipsilateral skin stimulus. In addition to flexion reflexes, local extension reflexes were mainly obtained from skin areas over extensor muscles. It is believed that these extension reflexes function as protective mechanisms by producing withdrawal of the heel, knee and buttock especially when the limb supports the body.