Wearable MCI to Reduce Muscle Co-activation in Acute and Chronic Stroke

Inclusion Criteria: Chronic stroke participants * Hemiparesis from first ever stroke at least 6 months prior to screening * Severe motor impairment (FMA of 7-30) * At least some voluntary shoulder and elbow muscle activation. Acute stroke participants * Hemiparesis from first ever stroke within the past 21 days * Severe motor impairment (FMA of 3-20), or total Manual Motor Score of 1-8 combined in Shoulder Abduction and Finger Extensors Exclusion Criteria: * Cognitive impairment with at least moderately impaired attention, or unable to follow instructions of the MCI task * Visual impairment (such as hemianopia) preventing full view of the screen * Anesthesia or neglect in the affected arm, or visual hemineglect (score of 2 on the NIH Stroke Scale Extinction and Inattention subtest). * Participation in another study on the affected arm within 6 weeks of enrollment or any pharmacological study * Inability to understand or follow commands in English due to aphasia or other reason * Diffuse or multifocal infarcts * Substantial arm pain preventing participation for 90 minutes a day * New spasticity treatment (pharmacological or Botox)