The purposes of this study were to compare the electromyographic activities from the rectus femoris, vastus medialis oblique portion, vastus medialis longitudinal portion, and vastus lateralis during straight leg raising (SLR) and quadriceps setting (QS) exercise and to determine which exercise is more effective to selectively strengthen the vastus medialis. Thirty two healthy subjects <19 men, 13 women) participated in the study. All participants performed SLR and QS exercises while electromyographic activity was recorded from EMG surface electrodes. Statistical analysis demonstrated significantly greater values for the vastus medialis oblique portion, vastus medialis longitudinal portion, and vastus lateralis activities during QS exercise than for those during SLR exercise. However, the rectus femoris muscle activity between SLR and QS exercises was not significantly different. The ratios of vastus lateralis to vastus medialis during SLR and QS exercise were not significantly different. These results show that QS exercise is more effective for strengthening the quadriceps muscle on the whole than the SLR exercise. As for selective methods of strengthening vastus medialis specifically, both SLR and QS exercises are useful.

The purpose of this study was to determine whether the vastus medialis oblique muscle(VMO) had greater electrical activity than the vastus lateralis muscle(VL) when hip adduction and knee extension exercise were performed. Electrical activity of the VMO and VL was measured on 42 healthy subjects (28 men, 14 women) during maximal voluntary isometric contractions of hip adduction and knee extension by an EMG-BIOFEEDBACK. The results showed that the electromyographic activity of the VMO was significantly greater than that of the VL during the hip adduction exercise. Differences noted with knee extension by performing hip adduction exercises. Isometric hip adduction exercises, therefore, may be advisable in the treatment of patients with patellofemoral pain.