Trunk kinematics is flexion/extension, medial/lateral flexion (i.e. respectively a lean to the left or right during the cutting maneuver to the left), and rotation to the left/right (i.e. respectively towards or opposite to the new movement direction during the cutting maneuver to the left). Left (L) and right (R) rectus abdominis, external oblique and erector spinae muscles during a bilateral contraction (L+R) or a unilateral contraction (L or R) yielded different trunk motion in 3D. Accordingly, directed co-contraction ratios (DCCR) served as information for trunk control. |