Effects of unilateral, bilateral in-phase and anti-phase modes of a functional task on non-paretic arm kinematics in acute stroke:

Introduction: Arm dysfunction is not confined to the contralesional arm. Understanding intralimb
kinematics of the non-paretic arm in stroke individuals provides insight to mechanisms of action
underlying bilateral upper limb training (BT). This study aimed to compare the effects of unilateral,
bilateral in-phase and anti-phase modes of a functional task on dominant/non-paretic arm kinematics in
healthy and acute stroke individuals respectively.
Methods: 7 healthy and 13 acute stroke individuals underwent 3D motion capture of unilateral,
bilateral in-phase and anti-phase modes of a functional grasp task. Intralimb kinematics was assessed
through movement time, peak velocity, movement smoothness and movement directness.
Results: In healthy individuals, dominant arm movement displayed no significant difference in any of
the intralimb kinematic measures between unilateral, bilateral in-phase and bilateral anti-phase grasp
task. In acute stroke individuals, non-paretic arm movement became significantly slower (Z ¼ 3.180,
p ¼ 0.001), jerkier (Z ¼ 3.184, p ¼ 0.001) and with lower peak velocity (Z ¼ 3.110, p ¼ 0.002)
during bilateral in-phase grasp task compared to unilateral task mode. Furthermore, in acute stroke
individuals, non-paretic arm movement became significantly slower (Z ¼ 3.181, p ¼ 0.001) and jerkier (Z ¼ 3.181, p ¼ 0.001) during bilateral anti-phase grasp task compared to unilateral task mode.
Conclusion: Bilateral in-phase and anti-phase task modes altered non-paretic arm kinematics in
stroke individuals, but not dominant arm kinematics in healthy individuals. Specifically, non-paretic
arm kinematics in stroke individuals became slower and jerkier during bilateral in-phase and anti-phase
grasp task compared to unilateral task modes. Kinematic responses to bilateral task modes is affected
by stroke. Therapists should note detrimental performance effects of bilateral training modes on the
non-paretic arm.