Elsevier

Applied Ergonomics

Volume 36, Issue 5, September 2005, Pages 547-555
Applied Ergonomics

Effect of computer mouse gain and visual demand on mouse clicking performance and muscle activation in a young and elderly group of experienced computer users

https://doi.org/10.1016/j.apergo.2005.03.003Get rights and content

Abstract

The present study evaluated the specific effects of motor demand and visual demands on the ability to control motor output in terms of performance and muscle activation. Young and elderly subjects performed multidirectional pointing tasks with the computer mouse. Three levels of mouse gain and three levels of target size were used. All subjects demonstrated a reduced working speed and hit rate at the highest mouse gain (1:8) when the target size was small. The young group had an optimum at mouse gain 1:4. The elderly group was most sensitive to the combination of high mouse gain and small targets and thus, this age group should avoid this combination. Decreasing target sizes (i.e. increasing visual demand) reduced performance in both groups despite that motor demand was maintained constant. Therefore, it is recommended to avoid small screen objects and letters. Forearm muscle activity was only to a minor degree influenced by mouse gain (and target sizes) indicating that stability of the forearm/hand is of significance during computer mouse control. The study has implications for ergonomists, pointing device manufacturers and software developers.

Introduction

At present, not only the young but also an increasing part of the elderly population uses computers and computer mice both at work and at home. Computer mouse work requires extensive hand-eye coordination skills and this fact combined with the well documented age related decline in fine motor control skills (Cooke et al., 1989; Ranganathan et al., 2001) is the background for a reduced performance during computer mouse clicking found in elderly (Laursen et al., 2001; Smith et al., 1999). Especially, when the demand for precision is increased the performance of the elderly is reduced. Therefore, the gain of the pointing device (e.g. the computer mouse) may also play a significant role for the degree of motor control required to perform computer mouse tasks. If the computer mouse gain is high, even small movements of the device have great impact on the amplitude of the screen cursor movements. Thus, adjustments of the mouse gain serve as a potential tool for optimization of performance and musculoskeletal workload in relation to age. In general, the physical demands during computer mouse tasks involve motor demands as well as visual demands. The level of the motor demands is dependent on the movement amplitude in combination with the demands for precision of the hand movements whereas the visual demands are determined by e.g. the size of the targets and their inter-distance on the monitor. These individual components of the physical demands have not been studied separately. Systematic combinations of computer mouse gain, sizes of screen targets and distances between targets make it possible to evaluate the specific effects of motor demands and visual demands on the ability to control motor output in terms of performance and muscle activation. Such results may help pointing device manufacturers, software developers, ergonomists and managers to optimize the conditions for the human when working at the computer.

It is hypothesized that performance will decrease with increasing motor demand even when the visual demand is kept constant. Furthermore, we anticipate that performance at different levels of motor demands will influence young and elderly differently due to an expected reduction in motor control in the elderly group. Secondly, it is hypothesized that increasing visual demands will not reduce performance if the index of difficulty according to Fitts Principle is kept constant and if the smallest screen objects are visually easy to detect.

The aim was to study the effect of various motor demands and visual demands on performance and muscle activation during computer mouse work in a young and an elderly group.

Section snippets

Participants

A total of 33 experienced computer users participated, 17 young (26.5±2.6 years. 9 females, 8 males) and 16 elderly (64.9±3.6 years. 8 females, 8 males). The young group had 6.3±2.8 years of experience using the computer mouse and the average computer use per week exceeded 20 h. The elderly had 7.3±4.0 years of experience and the average computer use per week exceeded 18 h. The Nordic questionnaire (Kuorinka et al., 1987) and additional questions regarding present health status were used to assure

Effect of motor demand on performance

Fig. 2A shows that the working speed was affected by the motor demand in the young group mainly expressed as a higher working speed at MG 1:4 at the large and medium target size. At the small target size a lower working speed of 13% and 9% in the young and elderly group, respectively, was found at MG 1:8 compared to the average working speed of MG 1:2 and 1:4. The level of motor demand did not influence the working speed of the elderly group at the larger target sizes. In general, the hit rate

Discussion

The present study demonstrated a rather complex relationship between computer MG and performance. Thus, the young subjects seem to have an optimum at MG 1:4 provided that the target sizes were large or medium. This optimum was not found among the elderly. Additionally, at the highest MG a decrease in working speed and hit rate was found for both age groups, especially when the target size was small. Thus, our hypothesis regarding the relation between performance and motor demand was confirmed

Conclusion

The study contributes to the understanding of the interaction between the physical demands involved in use of computer mouse, performance and muscle activation in relation to aging. In both age groups performance was reduced with increasing visual demands, indicating that computer mouse work with small screen objects and letters should be avoided if possible. The combination of small target sizes and high mouse gain reduced performance severely and this was especially pronounced in the elderly

Acknowledgements

We would like to thank the Danish Research Agency for supporting the project. Also we would like to acknowledge the technical assistance of Marianne Pilegaard, Institute of Exercise and Sport Sciences and Bjarne Laursen, National Institute of Public Health.

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