Abstract
The objective of this study is to locate the source of slowness in typing movements in subjects with spastic hemiparesis and to examine whether enlargement of keys would facilitate typing. Eleven subjects (mean age 17.1 years) being diagnosed as having spastic hemiparesis, most of whom as a result of cerebral palsy made fast reciprocal tapping movements with one finger of both hands separately within a ten seconds interval. Keys of 12 x 12 mm and 24 x 24 mm were used. Inter-key response interval (IRI), dwell time (interval in which the key is pressed) and forces were measured. Also, the standard deviation and coefficient of variation of the variables were calculated to determine regularity of the movements. The impaired hand tapped slower and more irregular and exerted less force. In addition, the duration of the dwell phase was lengthened for this hand. However, the percentage dwell time as a function of IRI was not different among both hands. Finally, enlargement of the keys shortened flight time ( = time in which the finger moves through the air from one key to the next) of the impaired hand, but not dwell time. From these results it is concluded that the entire movement is slower for the impaired hand. Disturbances are not exclusively located at the inversion of the movement. With respect to keyboard design, enlarged keys and a locked repeat function of the keys may be beneficial for subjects suffering from spasticity.
