Effect of Foot Position on Electromyographic Activity of the Vastus Medialis Oblique and Vastus Lateralis During Lower-Extremity Weight-Bearing Activities

Abstract

STUDY DESIGN: Repeated measures analysis of the effects of foot wedges on quadriceps muscle function. OBJECTIVES: To investigate the relationship between foot position and 2 quadriceps muscle activation conditions: maximum voluntary isometric quadriceps muscle contractions with the knee extended and 1-leg short squats with a knee flexion range of motion of 0 degree to 50 degrees. BACKGROUND: Abnormal foot position has been suggested as an important factor which may lead to patellofemoral malalignment. No previous studies have examined the effects of foot position on activation of the vastus medialis oblique (VMO) and vastus lateralis (VL) muscles using weight-bearing exercises. METHODS AND MEASURES: Sixteen healthy volunteers performed the 2 exercises under 3 foot conditions: level surface, a 10 degrees medial wedge, and a 10 degrees lateral wedge. Subjects' electromyographic data for the VMO and VL were analyzed using ANOVA. RESULTS: The normalized VMO/VL ratio was significantly greater during the short squat than during the maximum voluntary isometric muscle contractions, but no significant differences were identified across the 3 foot positions. CONCLUSIONS: Clinicians should understand that the benefit of using a foot orthotic to correct a pronated or supinated foot might not result from a change in quadriceps muscle activation intensity but from other mechanical factors.