Upper limb motor impairments are common. They affect quality of life and can lead to dependency. They are mainly due to neurological conditions such as stroke, multiple sclerosis, and traumatic spinal cord injury. However, the contractile properties of muscle, in particular the maximum force that can be generated voluntarily (MVF) depending on joint angle and motion speed, have been mainly studied and modeled in healthy people. This study aims at developing mathematical models describing residual muscle forces in patients with motor impairments. The knowledge could guide patients' rehabilitation and could be useful for the development of robotic assistance systems that use patients' residual capacities to control the level of assistance provided.

Inclusion Criteria:

• Patients aged between 18 and 85
• A patient who is a member or beneficiary of a social security scheme
• Patients hospitalised at the Saint-Hélier rehabilitation centre for a stroke more than 15 days old, MS or SCI
• Patients with a motor deficit ≤3/5 on the MRC (Medical Research Council) scale in both internal-external shoulder rotation and elbow flexion-extension.
• Patient with voluntary consent to participate in this study.

Exclusion Criteria:

• Spasticity >3/4 on the Aschworth scale in the shoulder abductor or elbow flexor muscles.
• Cognitive impairment that may interfere with measurements (MOCA < 20/30)
• Presence of a pressure sore > stage 2 at the ischial level
• Recent trauma to limbs or spine
• Decompensated heart disease or other unbalanced pathology which contraindicates or may hinder isokinetic testing.
• Persons deprived of their liberty by a judicial or administrative decision
• Pregnant women, women in labour or nursing mothers.