Electromyographic analysis of selected lower extremity musculature in normal subjects during ambulation with and without a Protonics knee brace

Abstract

Often, braces are an integral part of treatment programs for patients with pathology of the knee joint. Little evidence exists, however, as to the effect of braces on muscle function. The purpose of this investigation was to compare electromyography (EMG) from six lower extremity muscles during level walking without the Protonics knee brace and with the brace at eight resistance settings. Surface electrodes were placed on one lower extremity of 19 subjects (ages = 21-57) to evaluate EMG activity during ambulation with and without the knee brace. Data were normalized to maximum voluntary contractions and averaged across cycles. There was a significant increase in muscle activity of the rectus femoris, vastus medialis, and vastus lateralis muscles when the brace resisted knee extension and was set at the level of 9. Significantly higher EMG levels also occurred in the vastus lateralis and vastus medialis with the extension module set at level 6 when compared with the no brace trial and resistance levels set at 6 and 2 with the flexion module. In this normal population, there was an increase in activity of selected muscles when the brace was set at the highest resistance settings. These data serve as a guide for clinicians when considering incorporation of a brace of this type into patient management.