Elsevier

Applied Ergonomics

Volume 35, Issue 1, January 2004, Pages 21-28
Applied Ergonomics

Left-handed versus right-handed computer mouse use: effect on upper-extremity posture

https://doi.org/10.1016/j.apergo.2003.10.001Get rights and content

Abstract

Alternatives to reduce postural constraints have to be sought in order to reduce musculoskeletal complaints related to computer work. This study aimed at documenting the impact of using the mouse on the left side of a standard keyboard (with a right numeric keypad) on upper-extremity posture. A simulated computer task was performed by 27 subjects in a laboratory before and 1 month after ergonomics training. Shoulder flexion and abduction, as well as wrist extension were reduced with left-handed mouse use. Sixteen of the 27 subjects truly converted to using the mouse with the left hand. After a month of using the mouse with the left hand, the time required to perform the same task reduced, the perceived difficulty and discomfort improved, though the time to perform the task was still longer than when using the mouse with the right hand. For work involving both keyboard and mouse use, and without the need of the numeric keypad, it would probably be preferable to use a keyboard without the numeric keypad if the mouse is to be used on the right-hand side. If such keyboards are unavailable, an interesting alternative would be to use the mouse on the left side provided sufficient time is allowed to get accustomed to it.

Introduction

During the last decade, computer use has greatly increased both at home and at work. Moreover, graphic interfaces have become the standard, so the use of input devices, such as the computer mouse, have increased tremendously. Although the forces involved in manipulating input devices are usually small, postures adopted might put the users at risk of developing musculoskeletal disorders. Few studies have reported a possible association between frequent computer mouse use and neck-shoulder pain or pain in other regions of the upper-extremity (Aaras et al., 1998; Fernstrom and Ericson, 1997; Hagberg, 1995; Jensen et al. (1998), Jensen et al. (2002). Computer mouse use has been reported to involve shoulder flexion, abduction and external rotation (Karlqvist et al., 1994). It has also been shown that the use of a keyboard with a numeric keypad influences the mouse position by increasing the distance of the mouse with the sagittal plane of the body, therefore, requiring larger shoulder abduction, and increasing muscular load (Cook and Kothiyal, 1998; Karlqvist et al., 1998). Computer-work also involves the adoption of static postures for long periods of time. Even before the extensive use of the computer mouse, a relationship between weak static muscular contractions and musculoskeletal disorders has been proposed (Maeda, 1977; Westgaard et al., 1986). Shoulder flexion and abduction have also been identified as risk factors for neck and shoulder musculoskeletal disorders (Hagberg, 1981; Kilbom and Persson, 1987; Schuldt et al., 1987). The reduction of shoulder flexion and abduction during mouse work could help reduce the risk of developing musculoskeletal disorders in the shoulder region. Cook and Kothiyal (1998) proposed that the use of the mouse with the left hand could be an alternative for reducing shoulder posture constraints because the distance of the mouse hand to the midline of the body would be reduced.

With this strategy in mind, a large company in Canada implemented ergonomics training for their office employees, with one of its recommendations being the use of the mouse with the left hand. The idea behind this recommendation was to eliminate hand travel over the numeric keypad, thereby reducing the extent of motion when going from the mouse to the keyboard. Postural constraints on the shoulder, related to mouse use, would therefore be reduced.

The purpose of this study was to evaluate the advantages and disadvantages related to different mouse-use methods on postural constraints and performance, before and after an office ergonomics awareness training session (a 2-h small-group presentation on how to adjust an office workstation “ergonomically”, appropriate stretching exercises, and the rationale for recommending the use of the mouse with the left hand).

The main hypothesis of the study is that the use of the mouse with the left hand is an alternative for reducing postural constraints of the whole upper-extremity when using standard keyboard with a numeric keypad.

Section snippets

Subjects

Thirty-one office workers, who had not yet received the ergonomics training, volunteered to participate on the first session of measurements (baseline). Of these, 29 returned 1 month later (after the office ergonomics training) for the second session of measurements. Data from two subjects were lost because of technical problems, therefore the data of 27 subjects were used. There were 24 women (mean age: 42 yrs, range: 33–51 yrs; mean weight: 69 kg, range: 48–113 kg; mean height: 161 cm, range:

Results

The use of the mouse with the right hand and right mouse button (RR condition) did not result in any significant changes of posture or perception as compared to the left mouse button use (RL condition). Moreover there were no significant differences on any angles between the trials. Therefore the remainder of this section will focus on the comparison of the right hand, left button mouse use (RL condition) and the left hand, left button mouse use (LL condition). The results presented will be the

Methodological considerations

This study aimed at documenting the advantages and disadvantages of different techniques for using the computer mouse, relying essentially on a postural analysis of the upper-extremity on the side of the mouse. It is important to recognize that it is impossible from this study to establish if the reduction in postural constraints, as observed here, is sufficient to reduce the risk of developing or aggravating musculoskeletal disorders. A longitudinal evaluation could help document this aspect.

Conclusion

This study shows that use of the mouse on the left side as compared to the right side of a standard keyboard, reduces the postural constraints of the upper-extremity using the mouse. For work involving both keyboard and mouse use, and without extensive use of the numeric keys, it would probably be preferable to use a keyboard without the numeric keypad if the mouse is to be used on the right-hand side. If such keyboards are unavailable, use of the mouse on the left side is an interesting

Acknowledgements

This study was funded by the IRSST. The authors would like to thank Lucie Blais, Angiolina Mercuri, Christian Larue, and Pierre Desjardins for their support.

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