Physical exposure differences between children and adults when using standard and small computer input devices

By the age of five years, 75% of the children in the USA are using computers and at this age they are only one-half to two-thirds the size of and about one-fifth as strong as their adult counterparts. Fourteen children between five and eight years of age and their same-gender biological parents (giving a total of 28 subjects) were evaluated using both a standard and a smaller, child-proportional input device during standardised mouse and keyboard tasks. Typing and computer mouse performance were measured with tracking software, wrist posture was measured with an electrogoniometer and electromyography was used to measure finger flexor and extensor muscle activity in the right arm. With the small mouse, both children and adults performed the mouse task significantly faster and made significantly fewer errors. When using the standard-sized mouse and keyboard, children worked with significantly greater ulnar deviation and significantly less extension than their adult counterparts. When children used the smaller mouse, finger flexor muscle activity, finger extensor muscle activity and ulnar deviation significantly decreased, with little change in wrist extension compared to the standard mouse. No significant differences were observed between the standard and small keyboards for children or their parents. Compared to their adult counterparts, children had to apply twice the relative force, as a percentage of their maximum capacity, to activate the buttons and keys on the input devices. These measured differences may have application in the design of computer input devices for children.