Article

In previous studies, upper limb coordination was usually analyzed during
two-dimensional (2D) arm movements. Based on joint kinematics and muscle
activity, it has been demonstrated that the shoulder joint controls the
multi-joint movement. This study focused on three-dimensional (3D) reaching tasks
and examined if the coordination strategies previously described in 2D can be
transferred to 3D movements and if reaching to different locations in space has
an effect on kinematic and upper limb muscle strategies. Ten healthy subjects
reached to nine different targets in 3D space placed at arm length. Kinematic
data of the shoulder and elbow and electrical activity of 10 upper limb muscles
were registered. Differences in kinematics and EMG were compared between
different reaching conditions. Activity of shoulder muscles increased earlier
than elbow muscles inducing shoulder elevation prior to elbow extension. Reaching
at different widths only influenced shoulder kinematics, whereas reaching at
different heights influenced both shoulder and elbow joints. Modulation of
reaching height induced an immediate adaptation of elbow flexion followed by an
adaptation of shoulder elevation. As previously described in 2D, the shoulder
joint leads the movement during 3D reaching tasks. Changing the 3D nature of a
reaching task influenced the interaction between shoulder and elbow joint, with
reaching height primarily affecting the elbow coordination strategy.
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Langue : ANGLAIS