Frustrating Computer Users Increases Exposure to Physical Factors

J. Dennerlein, T. Becker, P. Johnson, Carson Reynolds, Rosalind W. Picard


We quantified physical measures of upper extremity stress, force, posture, and muscle activity as fourteen subjects completed a five page web-based survey. After completing one of the pages, the survey would prompt the user indicating they had completed that page incorrectly. Once acknowledged by the user, the system would redisplay the page with all of the user’s responses deleted. Responses to completing the page varied across individuals. Based on a subject’s response to a questionnaire, they were grouped into a high or low response group, with the high response group expressing more dissatisfaction with the page design. Force applied to the side of the mouse was higher (1.25N) for the 15 seconds after the display of the error message than the 15s before the error (0.88N) for the high response group (p=0.02). No difference was observed for the low response group. Similarly, the average wrist extensor muscle activity for both the ECR and ECU was 1 to 2 percent MVC higher for the 15s after the error message than compared to the 15s prior to the error for the high response group (p=0.01). Average activity was also 1 to 2 % higher for the second time completing the page compared to the first time. These results suggest that software design and usability can increase exposure to physical risk factors during computer work dependent upon a person’s assessment of ease of use.

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