The effects of patellar bracing on quadriceps EMG activity during isokinetic exercise

Patellofemoral pain syndrome is a prevalent ailment experienced by a number of individuals participating in regular physical activity. Little information is available concerning the effects of patellofemoral bracing on the function of the extensor mechanism in patellofemoral malalignment patients. The purpose of this study was to examine the effects of patellar bracing on the extensor mechanism in relation to isokinetic exercise. Sixteen subjects exhibiting patellofemoral pain symptoms were tested on an isokinetic dynamometer with and without a patellofemoral brace. The testing procedure involved three maximal concentric/eccentric quadriceps contractions at an angular velocity of 180°/s. Electromyographic (EMG) activity of the vastus medialis obliqus (VMO) and the vastus lateralis (VL) were recorded during testing. Integrated EMG activity (IEMG) was analyzed by a three-way ANOVA with repeated measures (P < 0.05). The results indicated that the application of the patellar brace resulted in a significantly smaller IEMG signal than during the non-braced condition in both the VMO and VL during both concentric and eccentric contractions (P < 0.05). The IEMG signal of the VMO was found to be significantly greater than the VL regardless of test or brace condition (P < 0.05). Moreover, the IEMG signal was also found to be significantly greater during the concentric contractions than the eccentric contractions during all testing conditions (P < 0.05). The clinical implication from this study suggests that muscle activation of the VMO and VL were reduced with the use of the brace. This type of bracing may provide mechanical support to the patellofemoral joint as evidenced by the reduction in quadriceps activation during isokinetic knee extension exercise.