The purpose of this study is to assess the impact of an isokinetic strength training of knee flexor and extensor muscles on walking performance in hemiparetic patients with knee extension thrust.

The study will be interventional single case experimental design (SCED) with multiple baseline design. SCED are experimental designs aiming at testing the effect of an intervention using a small number of patients using repeated measurements, sequential and randomized introduction of an intervention and method-specific data analysis, including visual analysis and specific statistics.

During baseline, patients will have a rehabilitation program in day hospital (4 days per week) with physiotherapy and physical activity and if necessary occupational and speech therapy. Isokinetic strength training will be added to this conventionnal rehabilitation program and will begin after 3, 4 or 5 weeks of baseline according to randomization

12 patients will be included in this study (6 patients in subacute stage and 6 in chronic stage ).

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

Due to the nature of the intervention neither subjects nor staff can be blinded to allocation. The outcome assessors and data analyst will be blinded to research aims and randomization (multiple baseline design before introducing isokinetic strength training)