Effects of Chair Arm Design on Wrist Posture

The effects of four different chair armrest designs on typing wrist posture were tested. Twenty-four subjects, men and women grouped at the 95th, 50th, and 5th percentiles for height, typed while sitting on each of four chairs with different armrests. The chair armrest designs investigated differed by the type, number and range of adjustments available. Each subject typed while instrumented with wrist electrogoniometers that measured wrist extension/flexion and radial/ulnar deviation. All conditions and tasks were counterbalanced. Results showed no main effects of chair armrest design on either wrist extension or ulnar deviation. Significant interactions involving chair armrest design were found for ulnar deviation but not for wrist extension. Correlations between anthropometric dimensions and wrist posture were found.