The effect of hip position and Emg biofeedback training on selectively increasing the vastus medialis oblique in relation to the vastus lateralis
Patellofemoral Pain Syndrome (PFPS) is a patellar tracking dysfunction usually associated with a muscular imbalance between the vastus medialis oblique (VMO) muscle and vastus lateralis (VL) muscle. The imbalance is most commonly attributed to a weak VMO resulting in a smaller VMO:VL ratio. Several electromyographic (EMG) studies have defined specific limb positions (such as external rotation of the hip) that preferentially activate the VMO. However, there has been no literature to show that preferential activation of the VMO successfully translates into increased VMO:VL ratios with training. The purpose of this study was to investigate the effects of hip rotation on the mean VMO:VL EMG ratio using EMG biofeedback over a 5 day training period. Thirty-six healthy female college students performed isometric quadriceps contractions, in terminal extension, with one of three hip positions: external hip rotation, internal hip rotation, and the anatomically neutral position. All participants were able to increase their VMO:VL ratio in 5 days regardless of hip position. Furthermore, external rotation of the hip was found to be a more effective position for the modification of the VMO:VL ratio than internal hip rotation. Exercises that incorporate external rotation of the hip, therefore, may be advisable in the treatment of PFPS.