This study will compare two treatments that may help participants recover after having suffered from stroke. Persons who experience weakness or paralysis of their arms/hands will be randomly placed in one of two groups. Each receives treatment five times a week for three weeks. One group will be treated with electrostimulation following a cyclic pattern (control treatment), the other group will be treated with electrostimulation triggered by nerve signals (i.e. stimulation starts when they deliberately try to move their arm (investigational treatment). Before and after the three weeks and additionally 12 weeks later, the ability to move the arm and hand will be documented with standardized tests.

Inclusion Criteria:

• First-time ischemic stroke with moderate arm paresis (Motricity Index - UE Sum-Score ≥ 40 ≤ 77 points) (Collin & Wade, 1990)
• Early to late subacute phase (7 days - 6 months) (Bernhardt et al., 2017)
• Existing ADL ability before the event (ICF d5 self-care, d6 domestic life, extent of problem ≤1 points) (WHO, 2001)
• Age ≥18 - 99 years
• Signed and dated ICF before the start of any study-specific procedure.

Exclusion Criteria:

• Lack of compliance with any inclusion criteria
• Implanted defibrillators, brain stimulators, pacemakers, medication pumps
• Therapy-resistant epilepsy
• Fever or infectious diseases
• Inflammatory or tumorous skin diseases in the stimulation area,
• Thromboses or vein inflammations
• Severe contractures of the affected extremity
• Wounds in the stimulation area
• Pregnancy
• Known allergic reactions to components of the investigational medical device
• Unstable psychological status
• Participation in other pharmacological clinical investigations within four weeks prior to enrolment
• Anything that, in the opinion of the Investigator, would place the subject at increased risk or preclude the subject's full compliance with or completion of the study