Lateral quickness is a crucial component of many sports. However, biomechanical factors that contribute to quickness in lateral movements have not been understood well. Thus, the purpose of this study was to quantify 3-dimensional kinetics of hip, knee, and ankle joints in side steps to understand the function of lower extremity muscle groups. Side steps at nine different distances were performed by nine male subjects. Kinematic and ground reaction force data were recorded, and net joint torque and work were calculated by a standard inverse-dynamics method. Extension torques and work done at hip, knee, and ankle joints contributed substantially to the changes in side step distances. On the other hand, hip abduction work was not as sensitive to the changes in the side step distances. The main roles of hip abduction torque and work were to accelerate the center of mass laterally in the earlier phase of the movement and to keep the trunk upright, but not to generate large power for propulsion.
Yuki Inaba (Corresponding Author) is with the Department of Life Sciences, University of Tokyo, Meguro, Tokyo, Japan. Shinsuke Yoshioka is with the Faculty of Sport and Health Science, Ritsumeikan University, Kusatsu, Shiga, Japan. Yoshiaki Iida is with the Department of Life Sciences, University of Tokyo, Meguro, Tokyo, Japan. Dean C. Hay is with the School of Physical and Health Education, Nipissing University, North Bay, ON, Canada. Senshi Fukashiro is with the Department of Life Sciences, University of Tokyo, Meguro, Tokyo, Japan.