Electromyographic activity evaluation of the patella muscles during squat isometric exercise in individuals with patellofemoral pain syndrome

The objective of this study was to compare the electromyographic (EMG) activity of vastus medialis obliquus (VMO), vastus lateralis longus (VLL) and vastus lateralis oblíquus (VLO) during wall slide squat isometric exercises at 45° (WS 45°) and at 60° (WS 60°) of knee flexion. Fifteen healthy control women and fifteen women with patellofemoral pain syndrome (PPS) participated in this study. The EMG activity was registered during WS 45° and WS 60° performed at maximal isometric voluntary contraction (MIVC) using surface differential electrodes connected to an EMG system. The EMG signals were analyzed using the root mean square (RMS) values and were normalized by MIVC obtained at 75° of knee flexion. To compare data between groups and exercises, the ANOVAtwo-way and Duncan post hoc tests were applied (p < 0.05). The results demonstrated higher EMG activity for all muscles studied at WS 60° when compared to WS 45° in both control and PPS groups. There were not significant differences between muscles during WS 60° in the control group, although a higher activity of VLL in relation to VMO and VLO was observed during WS 45° in control group. For the PPS group, no statistical difference was observed between muscles during both exercises. Thus, strengthening programs using WS 60° could be more effective for healthy women; however, both exercises could be indicated for rehabilitation programs aimed at women with PPS. In addition, the absence of significant differences between muscles in PPS group verified in this study suggests that muscle unbalance could not be a predisposing factor for PPS in women.