Stroke is the leading cause of disability in the United States. One of the reasons that it is so disabling is because of upper extremity hemiparesis (weakness in one arm), which is commonly seen after stroke.

The objective of this research is to see if a robotic system worn on the weakened arm like a brace is more useful in improving the strength and coordination of the affected arm, and those of other stroke survivors, than therapy only. Muscle weakness and lack of coordination after a stroke have great effects on how severely disabled the arm is and on quality of life after a stroke.

In this study, patients may be administered a new robotic brace as part of treatment for their affected arms. If they use this brace, your electromyography (EMG) signals will be used to control the powered arm brace. EMG signals are the small electrical signals that result from the actions of the muscles. The system will "listen" to patients' muscles, using small sensors that sit on top of the skin. The device will give the arm a "power-assist" when patients bend or straighten their elbows. The investigators want to test how easy and effective this system is to use. The investigators hypothesize that people using the robot will be more successful in their rehabilitative efforts - and that their movement will improve more - than people receiving traditional therapy.

Inclusion Criteria:

• Upper extremity Fugl Meyer score >10-< 25
• presence of volitionally activated EMG signal from the paretic biceps brachii of at least 5 ųV in amplitude
• stroke experienced > 1 month prior to study enrollment;
• a score > 24 on the Folstein Mini Mental Status Examination (MMSE)
• age > 35 < 85
• have experienced one stroke
• discharged from all forms of physical rehabilitation
• Myomo brace fits on affected arm properly and without discomfort (i.e., no red marks or discomfort observed in 10 minutes of use during fitting).

Exclusion Criteria:

• < 35 years old
• excessive pain in the affected hand, arm or shoulder, as measured by a score > 5 on a 10-point visual analog scale
• excessive spasticity at the affected elbow, as defined as a score of > 4 on the Modified Ashworth Spasticity Scale
• currently participating in any experimental rehabilitation or drug studies
• apraxia (< 2.5 on the Alexander scale)
• severe sensory loss in affected hand (Nottingham sensory scale at least 75% of normal)
• severe language deficits (score < 2 on NIH Stroke Scale question 9)
• Stroke that occurred in the brainstem
• A current medical history of uncontrolled cardiovascular, or pulmonary disease, or other disease that would preclude involvement in a therapeutic treatment
• History of neurological disorder other than stroke (other neurological disorders may affect the upper extremity motor performance of subjects.)
• Other significant pain or skin irritation in the upper extremity that would be exacerbated if by the use of the brace
• Substantial contracture of elbow, defined as > 20 degrees of elbow flexion, as measured at the baseline evaluation.