Medial and Lateral Quadriceps Muscle Activity during Weight-Bearing Knee Extension Exercise

Abstract

The purpose of this study was to determine the effect of weight-bearing terminal knee extension (WBKE) on normalized mean electromyographic (EMG) activity of the vastus medialis oblique (VMO) and vastus lateralis (VL) and the VMO/VL ratio. Sixteen subjects with no history of knee dysfunction participated. Surface EMG data were recorded from the VMO and VL of subjects' test legs as they performed the WBKE exercise under four conditions, three involving elastic resistance and one involving no elastic resistance. EMG data were normalized relative to a maximal isometric quadriceps contraction, and overall mean VMO and VL activity and the VMO/VL ratio were determined for all conditions. The three conditions utilizing elastic resistance showed higher mean VMO and VL activity than the no-resistance condition. The VMO/ VL ratio was not significantly altered during any exercise condition as compared to maximal, quadriceps setting exercise. WBKE against elastic resistance was superior to the same exercise without resistance for generating mean VMO and VL activity. Performance of the WBKE, regardless of the position of lower extremity rotation, does not selectively activate the VMO apart from, or to a greater degree than, the VL.

EMG Activation of the Vastus Medialis Oblique and Vastus Lateralis During Four Rehabilitative Exercises

“…These findings are similar to earlier studies, which reported no significant changes in EMG activity of the VMO and VL when the hip position was changed [8,17,20,34]. Other researchers have hypothesized that there will be an increase in VMO activity with external rotation of the hip because of the VMO's muscular fibers originating from the adductor magnus muscle.…”

“…However, based on a review of literature, there is still discrepancy as to which exercises best target the vastus medialis oblique (VMO) in comparison to the vastus lateralis (VL). Several variations to exercises have been studied, such as the effect of hip or tibial positioning [3,20], but as of yet no criterion method has been determined. Continued research should be done to further investigate commonly used quadriceps exercises in an effort to reach a higher standard of care for patients with PFPS.…”

Effectiveness of Elastic Resistance in Rehabilitation of Patients With Patellofemoral Pain Syndrome

“… 1 , 6 Adding elastic resistance to terminal knee extension exercise significantly increases vastus medialis obliquis and vastus lateralis activity. 25 Hopkins et al 10 analyzed leg pulls with surface electromyogram, noting higher levels of vastus medialis activity. 11 …”