Patellofemoral pain and the mechanomyographic responses of the vastus lateralis and vastus medialis muscles.

The purpose of this investigation was to examine the influence of patellofemoral pain (PFP) on the amplitude of the mechanomyographic (MMG) and electromyographic (EMG) signals from the vastus lateralis and vastus medialis muscles of the quadriceps femoris. Nine females reporting current signs and symptoms of PFP and 8 healthy females service as the control (CTL) group volunteered to participate in this study. Participants completed maximal and submaximal (25, 50, 75% MVC) isometric muscle actions of the quadriceps femoris at a leg flexion angle of 45 degrees below the horizontal plane of the lever arm. The involved limb for the PFP group and the dominant limb for the CTL group were selected for testing and all submaximal force levels were randomized. There was no (p > 0.05) group difference in EMG amplitude response for any muscle at any % MVC level. For the MMG amplitude, however, there was a main effect (p < 0.05) for group where the control group demonstrated greater MMG amplitude for each muscle. These findings suggest that the presence of PFP influenced mechanical aspect of muscle function as measured by MMG, but not the electrical properties (EMG). MMG may provide unique insight into the intrinsic effects on muscle function due to PFP.