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Ergovera's Ergo Savvy Newsletter )
 We help protect people, your company's most valuable asset March 2003 

In This Issue
That Pesky Mouse - Part 1
Research: Workload on the body and the mouse
New: Product and Software Evaluation
Credits and notices

Published by Ergovera Ergonomic Consulting to help you keep up on ergonomic innovations, so you can protect your employees and increase their productivity. Please pass it on to your colleagues and friends.

As I work on finishing up the first three chapters of my thesis on the computer mouse, a strange thing starts happening: the arm I mouse with is becoming fatigued and my shoulder is getting sore. These symptoms might be psychosomatic, but they are probably the effects of my increased workload.

Knowing risk factors as I do, I know that my symptoms are also probably related to the fact that I am a woman, have narrow shoulders, and have long arms with cold hands. As I read current research on the mouse, I realize that I need to make further ergonomic adjustments to my workstation: my forearm lacks support while I use a mouse on a keyboard tray.

While looking at some of the latest research on the mouse, I decided to focus on mouse placement, muscle loading, and individual differences in this month's issue.

There is now research to support anecdotal reports from computer mouse users of shoulder and arm discomfort. Unfortunately many of the recommendations from the studies I reviewed are not often seen in the real world (e.g., use of keyboards that do not have a built-in number pad, forearm support, etc.).

Until the year 2000, there had been a lack of objective data to support a causative link between mouse use and injury. However, a large Australian cross-sectional study of 270 computer mouse users in 2000 found a relationship between over-reaching or arm abduction (a position common with mouse use) and symptoms in the neck. The researchers concluded that use of the mouse could contribute to musculoskeletal injury.

The other two studies found similar results with specific muscles carrying higher workloads depending on the position of the mouse. Both of these studies used primary work surfaces for forearm support rather than the keyboard trays which are often seen here in the work place. One study used a height-adjustable table and the other used footrests as needed to position the subject at the correct height. The researchers found:

  • A large inter-individual variation in muscle loading.
  • That forearm support is a prerequisite for low muscular activity (especially in the trapezius muscle).
  • That optimal arm positioning is best achieved by use of a keyboard that does not have a built-in ten-key number pad.
  • That increasing the use of the keyboard (e.g., by using shortcut or control keys) is beneficial and induces more movement.

So, educate your employees on the use of shortcut keys to decrease their mouse use, teach them proper mouse techniques, and evaluate their forearm support. They may need forearm support from an armrest if they are using a keyboard tray.

Have a safe day,

Deidre Rogers, RN, MS, CAE

A study by Cook et al. examined the relationship between computer mouse use and musculoskeletal symptoms in 270 computer mouse users. They found a relationship between arm abduction (over reaching) with the use of the mouse and symptoms in the neck. Surprisingly, they did not find a relationship between hours of mouse use per day and reported symptoms. They also found relationships between non-mouse specific risk factors such as stress, screen height and shoulder elevation.

A Swedish experimental study (Bystöm et al.), found that overall electromyography (EMG) muscle load was low in CAD work, while the inter-individual variation between CAD users was considerable. According to the researchers, this indicated that the task performed was done in a variety of ways, and CAD users should be educated on proper working techniques. They concluded that the low muscular load occurred because subjects had well supported forearms. They found increased body movement and bilateral arm use with the CAD program that utilized shortcut and control keys rather than only the mouse. They recommend that the keyboard be used more frequently, since CAD work involves an extremely constrained work situation.

Another experimental study (Cook & Kothiyal) evaluated the position of the mouse when a standard keyboard is used, as well as when one without a built-in ten-key number pad is used. They found improved EMG levels (i.e., lower levels) in the anterior and middle deltoid muscles but not in the trapezius muscle with the mini-keyboard. The RULA measure they used also indicated better working posture with the mini-keyboard. They found poor wrist posture in all mouse positions and that all subjects rested their wrists on the desk while using the mouse. They also found a considerable variation in the inter-individual EMG levels of computer mouse users.


Cook, C., Burgess-Limerick, R., & Chang, S. (2000). The prevalence of neck and upper extremity musculoskeletal symptoms in computer mouse users. International Journal of Industrial Ergonomics, 26, (3), 347-356.

Cook, C., & Kothiyal, K. (1998). Influence of mouse position on muscular activity in the neck, shoulder and arm in computer users. Applied Ergonomics, 29, (6), 439-443.

Byström, J., Hansson, G., Rylander, L., Ohlsson, K., Källrot, G., & Skerfving, S. (2002). Physical workload on neck and upper limb using two CAD applications. Applied Ergonomics, 33, (1), 63-74.

Looking at utilizing a new product for a large group of employees? Ergovera has experience with a broad range of products and software. Save time and money by using our expertise to select the best priced, highest-value and most appropriate products.

Ergovera can help you with:

  • Choosing the most appropriate equipment.
  • Selecting break software and developing a stretching program for your employees.
  • When to use speech recognition software and when not to.
  • Which pointing devices work best, both for specific types of work and special individual circumstances.

Call Deidre at 831.335.8448 or send her a message now for more info about the class, rates and dates we could do the workshop at your site.

Copyright © 2002, Deidre Rogers and Ergovera Ergonomic Consulting. All rights reserved. Reuse in any form must be requested and granted in writing.

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