Effects of visual biofeedback using a laser beam on the EMG ratio of the medial and lateral vasti muscles and kinematics of hip and knee joints during a squat exercise

Abstract

[Purpose] The purpose of this study was to examine the effects of visual biofeedback on the EMG ratio of the medial and lateral vasti muscles and on the lower extremity joint angles during squat exercises performed by subjects with femoral anteversion. [Subjects] Seventeen subjects (5 men, 12 women) with femoral anteversion participated in this study. [Methods] Subjects performed a double-leg squat with and without visual biofeedback using a laser beam fixed to a patella strap. The peak angles of hip internal rotation and knee valgus were analyzed using a 3D motion analysis system, and the vastus medialis oblique/vastus lateralis (VMO/VL) activity ratio was calculated using the value recorded by surface electromyography during the squat exercises. [Results] Significant decreases were found in the hip internal rotation angle and knee valgus angle, and a significant increase in the VMO/VL activity ratio was observed on the dominant side when performing a double-leg squat with visual biofeedback using a laser beam. [Conclusions] We suggest that laser-beam visual biofeedback would be used as an effective for improving VMO muscle strength and reducing the angle of hip internal rotation and knee valgus during squat exercises.