Article

Up to 60% of individuals with moderate to severe chronic hemiparetic
stroke experience excessive involuntary wrist/finger flexion that constrains
functional hand movements including hand opening.
It's not known how
stroke-induced brain injury impacts volitional hand opening and grasping forces
as a result of the expression of abnormal coupling between shoulder abduction and
wrist/finger flexion or the flexion synergy. OBJECTIVE:
The goal of this study is
to understand how shoulder abduction loading affects volitional hand opening and
grasping forces in individuals with moderate to severe chronic hemiparetic
stroke. METHODS: Thirty-six individuals (stroke, 26; control, 10) were recruited
for this study. Each participant was instructed to perform maximal hand opening
and grasping forces while the arm was either fully supported or lifted with a
weight equal to 25% or 50% of the participant's maximal shoulder abduction
torque. Hand pentagon area, defined as the area formed by the tips of thumb and
fingers, was calculated during hand opening. Forces were recorded during
grasping. RESULTS: In individuals with moderate stroke, increasing shoulder
abduction loading reduced the ability to maximally open the hand. In individuals
with severe stroke, who were not able to open the hand, grasping forces were
generated and increased with shoulder abduction loading. Stroke individuals also
showed a reduced ability to control volitional grasping forces due to the
enhanced expression of flexion synergy. CONCLUSIONS: Shoulder abduction loading
reduced the ability to volitionally open the hand and control grasping forces
after stroke. Neural mechanisms and clinical implications of these findings are discussed.

Langue : ANGLAIS