The Effect Of Knee Joint Angle Difference On The Compartment Neuromuscular Activation In Rectus Femoris

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Bi-articular muscles play an important role to smooth movement in human. However, the biomechanics and physiological function of those muscles is unclear. Thus, this study investigates the function of rectus femoris as a famous bi-articular muscle in lower limbs. PURPOSE:The purpose of this study is to unravel the compartment neuromuscular activation of rectus femoris during isometric knee extension and hip flexion in different knee angles. METHODS:Subjects were eight healthy men. Knee extension with hip flexion were performed in isometric contraction. Knee angle was set up at 90, 60, 30, and 0 degree. Also, there were three contractions as follow: Maximum voluntary contraction (MVC), 80%MVC and 60%MVC. Muscle activation of rectus femoris was measured by using multi-channel surface electromyography, and calculated the average rectified value (ARV). We evaluated the ARV of rectus femoris divided into proximal, medium and distal compartment. We evaluated the ARV of rectus femoris divided into proximal, medium and distal compartment. RESULTS:In the proximal region at 30 degrees knee angle, averaged ARV value in the MVC (0.113 mV) was significantly higher than those of other two contraction groups (80%MVC: 0.071 mV, p<0.05 vs MVC; 60%MVC: 0.047 mV, p<0.01 vs MVC). There was no significant differences in ARVs both in medium and distal compartments. CONCLUSIONS:Proximal region of rectus femoris has the role of knee extension and hip flexion in slightly flexed knee joint position. We conclude that the difference of knee angle affects the compartment neuromuscular activation in rectus femoris.