DIFFERENCE OF KNEE ALIGNMENT EFFECT ON VASTUS MEDIALIS AND VASTUS LATERALIS DURING THE LEG PRESS EXERCISE

Abstract

Lateral subluxation of the patella or frank lateral dislocation may be the result abnormal musculoskeletal architecture. It is hypothesized that in some of these patients there is a relative imbalance between the vastus medialis and the vastus lateralis muscles. PURPOSE The purpose of this study was to investigate knee alignment differences between the normal knee and the genu varum knee by measuring electromyographic(EMG) activities of the vastus medialis and vastus lateralis muscles during leg press exercise in 75%1RM. METHODS Four individuals with normal knees and five with genu varum performed the leg press using narrow, medium and wide stances with a load of 75%1RM. Surface EMG(1000Hz) data were collected from the vastus medialis and vastus lateralis. Integrate EMG (iEMG) value were calculated for each muscle during each repetition. RESULTS In both groups, the vastus medialis muscle measurement was higher than the vastus lateralis muscle measurement for each stance during leg press. The iEMG values of the vastus medialis were 15.9% greater than the vastus lateralis for the genu varum group and 42.6% greater for the normal knee group during the leg press using a narrow stance. Using a medium stance, the iEMG values of the vastus medialis were 19.0% greater than the vastus lateralis for the genu varum group and 34.5% greater for the normal knee group. Using wide a stance, the iEMG values of the vastus medialis were 19.0% greater than the vastus lateralis for the genu varum group and 34.5% greater for the normal knee group. CONCLUSION The results suggest that the electromyographic activity of the vastus medialis muscle was significantly greater than that of the vastus lateralis in the both groups during the three stances. However, for the genu varum group the difference of the iEMG values between the vastus medialis and vastus lateralis was greater than for the normal group. The imbalance between the vastus medialis and vastus lateralis muscles with genu varum may be improved by using a wide stance when persons with genu varum perform leg presses.