TITLE:
Joint Coordination Organizes to Form the Task-Dependent Trajectory of the Body Center of Mass
AUTHORS:
Yoichiro Sato, Hiroshi Nagasaki, Norimasa Yamada
KEYWORDS:
Joint Coordination, Trajectory Formation, Task-Dependent, Whole-Body Motion
JOURNAL NAME:
Journal of Behavioral and Brain Science,
Vol.6 No.1,
January
14,
2016
ABSTRACT: 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.