The rehabilitation intensity and frequency of upper extremities of stroke patients is insufficient. Virtual reality technique may solved this problem. The investigators want to build up the motion trajectory system by head-mounted display virtual reality technique, and to explore the effect of visual feedback on motion trajectory in a virtual reality environment.

How to increase the rehabilitation intensity in the critical rehabilitation window for stroke patients (half year since onset) was very important. The training intensity and frequency of upper extremities is insufficient. The proprioceptive neuromuscular facilitation (PNF) movements of upper extremities are applied to all daily upper extremities movement. The goals of this study are that the investigators want to build up the motion trajectory system by head-mounted display virtual reality technique, and the investigators want to explore the effect of visual feedback on motion trajectory in a virtual reality environment. The investigators will record the motion patterns, motion trajectory and the deviation of position and angle comparing to the normal PNF movement pattern to analyze the motion accuracy.

Stroke patients Inclusion criteria

1. Age:20~100y/o.
2. Stroke onset time > 1 week, and neurological status and medical condition are stable.
3. Brunnstrom stage III to V.
4. Can follow order.

Exclusion criteria

1. Crucial organ failure, including heart, lung, liver, and kidney.
2. Brain operation and epilepsy.
3. Severe metal illness and aphasia, so cannot follow order
4. Feel uncomfortable while using virtual reality.
5. Crucial eye problems, including color-blind, weak color, cataract, glaucoma, etc.
6. Mental illness, neuro-musculoskeletal system lesions, vertigo, claustrophobic.
7. Illness and pain to affect upper extremities movement.

Healthy people Inclusion criteria

1. Age:20~100y/o.
2. No pain to affect upper extremities movement.

Exclusion criteria

1. Feel uncomfortable while using virtual reality.
2. Crucial eye problems, including color-blind, weak color, cataract, glaucoma, etc.
3. Cognition impairment, history of mental illness, neuro-musculoskeletal system lesions, vertigo, claustrophobic.
4. Epilepsy.

Stroke patients Healthy people