Kinematic analysis of the lower limbs in different squatting conditions

Abstract

The purpose of this study was to show the relationship and the definite flexion angle proportion among the lower limb joint angles and the characteristics of muscle activity in different squatting conditions. The subjects were eight healthy men. Exercise tasks were squatting in three CFP （center of foot pressure） positions; 1:neutral, 2:forward and 3:backward. As a result, the relationships between two specific flexion angles（ knee joint vs. hip joint, and ankle joint vs. hip joint） were shown in linear regression equation in every CFP position. The flexion angle proportion of the knee and ankle joint angle to the hip joint angle （knee to hip ratio, ankle to hip ratio） remained constant, but the value differed according to the CFP positions. The above mentioned proportions were 1.1 and 0.4 respectively in conditions 1 and 2, but were 0.9 and 0.2 in conditions 3. Muscles activity of rectus femoris, vastus medialis, vastus lateralis, and tibial anterior effectively increased throughout the motion in every condition. There was a difference among the motions only in the tibial anterior. The muscle activity was significantly higher in order of conditions 2,1,3. The above results suggest that there were the definite flexion angle proportions between lower limb joint angles during squatting, but the value of flexion angle proportion differed depending on the CFP positions and the value of the backward squatting was smaller than the value of the neutral and forward squatting.