Novel Training Environment to Normalize Altered Finger Force Direction Post Stroke

Despite the functional importance, fingertip forces are rarely explicitly addressed with feedback in therapy. This gap in treatment is due to a lack of tools to provide explicit feedback on patients' volitional finger force generation. To address this unmet need, the investigators developed a novel tool for practice of volitional three-dimensional (3D) force generation with explicit feedback. The objective of this project is to determine if 3D finger force training is an effective tool in restoring hand function post stroke.

Stroke survivors with moderate to severe hand impairment with at least palpable volitional grip force will randomly be assigned to either the experimental or control group, stratified by impairment level. Both groups will undergo 3 1-hr training sessions per week for 6 weeks in which they practice volitional finger force generation against force sensors. The experimental group will practice for various target force directions to explore the 3D force workspace and receive feedback in 3D force, while the control group will practice 1D force generation without feedback on other directional forces on a computer screen.

Training will progress by increasing influence of flexion synergy by varying posture requirements and increasing force level, introducing feedback delay, and incorporating unilateral/bilateral activity. Evaluation will occur at baseline (3 times over 3 weeks to establish baseline trends) and every 2 weeks during 6-week intervention to determine pattern of progress, and at 1-month follow-up to assess retention.

Inclusion criteria

• Survived a stroke at least 3 months ago
• Moderate to severe hand impairment (Chedoke-McMaster Hand Stage 2-4)
• Ability to generate palpable volitional grip force upon cue
• Sufficient cognitive ability to participate (NIH Stroke Scale, NIHSS, Questions and Commands score = 0-1)
• Ability to recognize all quadrants of the visual field (NIHSS Visual Field Test score = 0)

Exclusion criteria

• Concurrent upper limb rehabilitation
• Inability to follow 2-step commands
• Severe muscle tone prohibiting passive movement of the fingers or proper placement of the fingers on the force sensors as needed to participate in the training (Modified Ashworth Scale=4-5 out of 5)
• Change in spasticity medication or botulinum toxin injection in the upper limb within 3 months prior to or during enrollment
• Total sensory loss on fingertips (NIHSS Sensory score=2)
• Comorbidity (e.g., orthopaedic conditions that limit ranges of motion, premorbid neurologic conditions)
• Language barrier or cognitive impairment that precludes providing consent