MUSCLE ACTIVATION UNDER DIFFERENT ANKLE AND KNEE POSITIONS DURING LEG EXTENSION EXERCISE

BACKGROUND: The imbalance between vastus medialis oblique (VMO) and vastus lateralis (VL) is one of the mean factor for (PFPS) onset, related to improper alignment of the patella. PURPOSE: The aim of this study is to investigate the effects of knee flexion, knee rotation and ankle flexion attitudes on the activity of the VMO and VL muscles during unilateral maximal voluntary isometric contraction (MIVC) of the quadriceps femoris. METHODS: Ten healthy subjects volunteered for the study. Five conditions for two different knee flexion angles (90°; 30°) were tested: neutral condition, maximal knee medial rotation, maximal knee lateral rotation, maximal ankle plantarflexion and maximal ankle dorsiflexion. Data were normalized in order to calculate the normalized VMO/VL ratio. CONCLUSIONS: The normalized VMO/VL ratio for all the conditions occurred at 90° of knee flexion was higher than the same conditions at 30° of knee flexion (p=0.04), due to a lower level of activity of the VMO. No statistically differences between conditions at the same knee angle were observed, with only exception for lateral rotation at 30° knee flexion (p<0.05). These findings suggest that knee flexion is the main factor to be considered to improve VMO activity during leg extension exercise