Author(s)

Yoichiro Sato¹, Hiroshi Nagasaki², Norimasa Yamada³

¹Department of Physical Therapy, Faculty of Health Sciences, Hokkaido University of Science, Sapporo, Japan.
²Faculty of Medical Science and Welfare, Tohoku Bunka Gakuen University, Sendai, Japan.
³Department of Sport and Physical Education, Chukyo University, Toyota, Japan.

As the central nervous system controls whole-body motion, which involves multi-joint movement, certain problems with regard to the number of variables controlled by the central nervous system arise (i.e., the “degree of freedom problem”). The central nervous system solves these problems not by controlling joint movements, but rather by controlling only the task-dependent center of mass (COM) position of the whole body. Although uncontrolled joint movement should be organized in a coordinate manner to form the task-dependent COM position, it is unclear what kind of law joint coordination is organized by. Hence, in the present study, we aim to clarify the shape of joint coordination by elucidating the mutual relationship between the COM trajectory and joint movement during whole-body motion. Downward squatting motions with five trunk angles are recorded by using a 3-D motion analysis system in 8 healthy males. The COM trajectory shows a task-dependent path in all trunk conditions. The shank angle decreases with an increase in the trunk angle to produce the task-dependent COM trajectory, whereas the thigh showsd a constant angle. These findings demonstrate that the COM trajectory is constrained by biomechanical dynamics and minimum muscle torques, and that the joints are organized into a lawful coordinative structure to form the COM trajectory.

Joint Coordination, Trajectory Formation, Task-Dependent, Whole-Body Motion

Sato, Y. , Nagasaki, H. and Yamada, N. (2016) Joint Coordination Organizes to Form the Task-Dependent Trajectory of the Body Center of Mass. Journal of Behavioral and Brain Science, 6, 1-8. doi: 10.4236/jbbs.2016.61001.