Inclusion Criteria for Healthy able-bodied volunteers:  18-39 years old, men and women  Inclusion Criteria for Right-handed Post-stroke adults:  21-75 years old Right-handed Longer than 6 months post-stroke Persistent hemiparesis on the right upper extremity (UE) Residual UE voluntary movement as indicated by a score of 1-3 on the motor arm item of the NIH Stroke Scale (NIHSS) and a score of 19-55 on the UE portions of the Fugl Meyer Assessment (UE-FMA) Preserved cognitive function Ability to follow and read simple instructions as indicated by a score of 1 or above on item #9 on the best language items of the NIHSS  Exclusion Criteria for both healthy and post-stroke individuals: To ensure the safety associated with TMS, the following adults will be excluded (*, not applicable to post-stroke subjects):  Had an adverse reaction to TMS. Had epilepsy or seizure. Have any implanted devices such as a neurostimulator or cochlear implant. Had a stroke or lesion (including tumor) in your brain*. Had a head injury or brain surgery*. Suffer from frequent or severe headaches. Had a fainting spell or syncope. Have any metal in the head such as shrapnel, surgical clips, or fragments from welding or metalwork. Have any implanted device such as cardiac pacemakers, medical pumps, or intra-cardiac lines. Had any brain-related conditions*. Had any illness that caused brain injury* (i.e. meningitis, aneurysm, brain tumor). Had any head trauma that was associated with a loss of consciousness or diagnosed as a concussion. Being treated for any psychiatric condition (i.e. depression, anxiety, PTSD, schizophrenia). Had more than 2 cups of coffee/caffeinated beverages in the last 12 hours. Had more than 2 alcoholic beverages in the last 12 hours. Had less than 6 hours of sleep in the last 24 hours. Suspected of pregnancy.  Additional Exclusion Criteria for post-stroke adults:  A first stroke less than 6 months or more than 24 months prior to the participation. Hemiparesis on the left side. Hemorrhagic stroke. Cerebellar stroke. Severe sensory impairment as indicated by the score of 2 (Severe to total sensory loss; the patient is not aware of being touched in the face, arm, and leg) in item #8 (Sensory) of the NIH Stroke Scale (NIHSS). Serious uncontrolled medical conditions. Severe apraxia of speech. Excessive pain in any joint of the more affected extremity that could limit the ability to cooperate with the intervention, as judged by the examining clinician. Receiving any anti-spasticity drugs orally at the time of expected participation, 3 months prior, or wish to or is scheduled to receive injections prior to study completion. Received phenol injections less than 12 months prior to receiving therapy. Unable to stand independently for 2 min., transfer independently to and from the toilet, or perform sit-to-stand. A score of less than 24 on the Folstein Mini-Mental State Examination. Passive range of motion less than 45 degrees for abduction, flexion or external rotation at the shoulder, or pronation of forearm; or greater than 30 degrees flexion contracture at any finger joint. Active range of motion less than 10 degrees for finger flexion or extension. Inability to volitionally activate right UE proximal muscles used for EMG placement. Clinical judgment of a) a major medical disorder that substantially reduces the likelihood that a subject will be able to comply with all study procedures, b) unable to successfully perform all rehabilitation exercise test examples, or c) unable or unwilling to perform study procedures/therapy, or expectation of non-compliance with study procedures/therapy. No TMS response in the first dorsal interosseous muscle in the right hand.