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Patellofemoral pain syndrome is a patellar tracking dysfunction usually associated with vastus medialis oblique (VMO) weakness, and subsequently, a small VMO: vastus lateralis (VL) ratio. Several early electromyographic (EMG) studies have defined specific limb positions (such as external rotation of the hip) that preferentially activate the VMO. However, whether preferential activation of the VMO successfully translates into increased VMO:VL ratios with training has not been investigated. The purpose of our study was to investigate the effects of hip rotation on the mean VMO:VL EMG ratio using EMG biofeedback training over a 5-day period.
Subjects performed isometric quadriceps contractions, in terminal extension, in 1 of 3 hip positions: the anatomically neutral hip position (group A), external hip rotation (group B), and internal hip rotation (group C). Pretest to posttest data were analyzed with a 3 (group) × 2 (test) analysis of variance with repeated measures on the last factor.
Thirty-six healthy female college students with no known right knee musculoskeletal dysfunction.
Activity of the VMO and VL was recorded by EMG and reported as the VMO:VL ratio.
The main effect for group was not significant, but the main effect for test was significant. No significant interaction between group and test was noted.
The statistical analysis of our results suggests that hip position during EMG biofeedback training has no effect on the VMO:VL ratio. However, because subjects were able to significantly increase their VMO:VL ratio in 5 days regardless of hip position, EMG biofeedback can be recommended for the facilitation of VMO muscular recruitment.