Muscle weakness is a common outcome after stroke and is usually especially large on one (more affected) side. Rehabilitation to improve strength requires attempts to get stronger, but strength can improve in more than just the target that is trained.
Over 100 years ago, Edward Scripture discovered this “cross-education”, a phenomenon where training one limb improves the strength in similar muscles on the untrained side.
Cross-education strength training has been confirmed in many muscles and with many protocols. The strength gain on the other, untrained side is less than the trained side, though.Read more on psychologytoday.com