A New Approach to the Evaluation of Local Muscular Load while Typing on a Keyboard

The aim of this study was to assess the contribution of using keystroke dynamics (KD) in combination with integrated electromyography (iEMG) for the objective evaluation of local muscular load of hands and forearms while typing on a computer keyboard and to compare it with results of the commonly used method.

Study was performed on 12 subjects. Data were collected using our own application for capturing KD data and using EMG Holter for detecting electromyographic potentials to determine local muscular load.

The results of our study revealed that currently used methods for assessment of the workload while typing on a computer keyboard are not entirely accurate. In particular, the real total number of keystrokes performed during processing of a text is significantly higher than the count of characters the text is consisting of. In addition to this count, also the so-called invisible keys, keyboard shortcuts, and especially corrections in the typed text must be taken into consideration.

The results indicated that all probands in our study exceeded the valid hygienic limits for the total amount of the small repetitive movements of the hands and forearms and the total amount of the keyboard typing movements. Most of the probands in our study also exceeded the valid hygienic limit for the highest average time-weighted value of the percent maximum voluntary contraction (%MVC). This implies that the keystroke dynamics method has a great potential to increase the accuracy of evaluation of local muscular load when using the keyboard and thus to improve the existing methodology for investigation of occupational diseases resulting from overload while working on the computer.