Prior to the experiment, the subject provided basic biographical information. The investigators then explained the experimental process and demonstrated the operation of the device. For usability assessment, the subject operated the device under the instruction by the researchers, during which problems observed and questions asked were recorded. Following device operation, the subjects filled the system usability scale (SUS) questionnaire that obtained subjective evaluations and recommendations for the device. Experimental instrument consisted of the rehabilitation device, video cameras, still image cameras, digital voice recorders, questionnaires and observational recording forms.