Isokinetic Strength Training in Hemiparetic Patient With Knee Extension Thrust

Inclusion Criteria: * Hemiparetic patient (hemorragic or ischemic stroke) * Subacute stage (\< 6 Months) ou chronic stage of stroke (\> 6 months) (6 patients in each group) * Age between 18 and 75 years * Able to walk 10 meters independently without any assistive devices * Knee extension thrust during stance phase of gait cycle (rapid posterior movement of the knee toward extension) * Scheduled rehabilitation program with isokinetic strength training * affiliation to a social security * Patients who received and signed informed consent Exclusion Criteria: * Major comprehension deficit that not allow to give informed consent and participate to isokinetic strength training (assessed with comprehension subscore of Langague screening Test) * non stable (unstable cardiovascular condition) * musculoskeletal disorders with knee pain that not allowed isokinetic strength training * Botulinum toxin injection less than 3 months or repeated injection in lower limb, * Proprioception trouble assessed with proprioception section of the Fugl-Meyer Assessment \[FMA-P\] 0/2 * spasticity of triceps surae ≥2 (Modified Ashworth scale) * ankle dorsiflexion angle less than 90° * pregnant women or breastfeeding * persons with safety measure