Article

Although global movement abnormalities in the lower extremity poststroke have
been studied, the expression of specific motor impairments such as weakness and
abnormal muscle and joint torque coupling patterns have received less attention.
We characterized changes in strength, muscle coactivation and associated joint
torque couples in the paretic and nonparetic extremity of 15 participants with
chronic poststroke hemiparesis (age 59.6 +/- 15.2 years) compared with 8
age-matched controls. Participants performed isometric maximum torques in hip
abduction, adduction, flexion and extension, knee flexion and extension, ankle
dorsi- and plantarflexion and submaximal torques in hip extension and ankle
plantarflexion. Surface electromyograms (EMGs) of 10 lower extremity muscles were
measured. Relative weakness (paretic extremity compared with the nonparetic
extremity) was measured in poststroke participants. Differences in EMGs and joint
torques associated with maximum voluntary torques were tested using linear mixed
effects models. Results indicate significant poststroke torque weakness in all
degrees of freedom except hip extension and adduction, adductor coactivation
during extensor tasks, in addition to synergistic muscle coactivation patterns.
This was more pronounced in the paretic extremity compared with the nonparetic
extremity and with controls. Results also indicated significant interjoint torque
couples during maximum and submaximal hip extension in both extremities of
poststroke participants and in controls only during maximal hip extension.
Additionally, significant interjoint torque couples were identified only in the
paretic extremity during ankle plantarflexion. A better understanding of these
motor impairments is expected to lead to more effective interventions for
poststroke gait and posture.

Langue : ANGLAIS