Change of Quadriceps Muscular strength and Muscle Activity According to Knee Extension Angle and body Mass Index Kim Su-Min1, Sim Eun-Ju1, Lee Dong Yeop2, Yu Jae Ho2, Kim Jin seop2, Hong Ji Heon2,* 1Student, Dept. Physical Therapy, Sun Moon Univeresity, Asan-si, Republic of Korea 2Professor, Dept. Physical Therapy, Sun Moon Univeresity, Asan-si, Republic of Korea *Corresponding Author: Ji Heon Hong, Professor, Dept. Physical Therapy, Sun Moon Univeresity, Asan-si, Republic of Korea, Email: hgh1020@hanmail.net
Online published on 8 August, 2019. Abstract The purpose of this study was to investigate the effect of body mass index (BMI) on muscle strength and activity according to the knee angle. Muscle activity of vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF) was measured for 48 healthy adults. Isokinetic equipment was used to measure the isometric strength of the knee extensors at 0°, 30°, 60°, and 90° flexion. One-way ANOVA was used to compare isometric muscle strength and activity. The maximum isometric strength of the knee extensors according to the knee angle showed a significant difference between the groups at 0°, 30°, and 90° of knee flexion (p<.05). The maximum isometric strength at 0° flexion of the knee joint was significantly different between the normal and overweight, and the underweight and overweight, respectively. In knee flexion 30°, there was a significant difference between underweight and normal, underweight and overweight. In 90° flexion, there was a significant difference between the underweight and the overweight. There was a significant difference in VM at 0° and 30° knee flexion (p <.05). Post hoc test results showed a significant difference between underweight and overweight at 0° flexion. In 30° flexion, there was a significant difference between normal and overweight, and between underweight and overweight. It is considered that selective muscle strengthening according to a specific angle is necessary according to BMI. Top Keywords Body mass index, EMG, Isometric contraction, Knee extensors, quadriceps. Top |