Muscular loading and subjective ratings of muscular tension by novices when typing with standard and split‐design computer keyboards

Abstract

The objective of this research project was to compare two different computer keyboard designs with respect to their effect on the extent of muscular loading in the right and left trapezius and extensor muscles during typing. The two computer keyboards used in this study were (1) a classic or standard keyboard, and (2) a split‐design keyboard. Evaluation of muscular loading was done using the electromyography (EMG) technique and subjective ratings of muscular tension. Sixteen women, between 18 and 26 years of age, with similar secretarial experience and limited typing abilities, took voluntary part in the experiment. Each subject used both keyboards for 15 min. The EMG signals recorded during typing sessions were those of the left and right sides of trapezius (m. trapezius pars descendeus) and extensor (m. extensor carpi radialis brevis et longus) muscles. Upon completion of each task, subjects were asked to evaluate perceived levels of muscular tension in the shoulder‐neck area and forearms. The results showed that the split‐design computer keyboard significantly reduces muscular loading of the trapezius muscle and subjective feelings of muscular tension in the shoulder‐neck area.