A weblog dedicated to Ergonomics education, dicussion and debate. This emerging field has the power to transform industry, business and the lives of ordinary people for the better. The Industrial Athlete intends to encourage and document our profession's vision of an ergonomically-friendly future!

Sunday, February 19, 2006

Sunday Spotlight: The Computer Mouse

After the chair, one of the most often used implements in today's office is the computer mouse. Pictured above is a typical mouse with no-frills or amenities. It is because of its design and increased use however, that it can contribute to the development of Carpal Tunnel Syndrome (Source: Ergonomics, Volume 42, Number 10, pg 1350 - 1360), among other aggravations.

The rise of the body of the mouse relative to the work surface causes the user to put their wrist into sustained extension, narrowing the carpal tunnel within the wrist. With the use of the fine muscles in the forearm to perform mousing tasks, the tendons from those muscles rub against the ligaments and the median nerve, causing inflammation in the tendons, subsequently causing compression of the median nerve, and thus, the symptoms that characterize Carpal Tunnel Syndrome.

Additionally, a standard mouse with a trackball bottom tends to get dirty on a regular basis, resulting in increased effort to move the mouse, and wasted time spent cleaning the insides of the mouse to restore responsiveness. Ironically, the latest advances in mousing technology have created new problems in spite of "solving" the old issues. Wireless mice drain the batteries that they run on fairly quickly, thus not solving the wasted time issue; it is plausible that they may have made it even worse, especially if a fresh supply of batteries is not readily at hand!

In light of the issues addressed above, here is some general infomation and advice to keep in mind when obtaining a mouse:

  • Ideally, a vertical mouse or a pistol-grip mouse should be acquired. These mice require the user to keep their wrists in a neutral orientation (i.e. the "handshake" position) in order to be operated.
  • The mouse that you use should be an optical mouse, and those of the wired variety. This ties the mouse to a constant power source, eliminating the maintenance issues of the old trackball mice and wireless mice. Any issues with the wire can be minimized by keeping the hard drive close enough to the user so that there is enough slack, avoiding a "tug of war" between the user and the hard drive.
  • The mouse should be positioned so that the user does NOT have to reach for it. The mouse should be right in the palm of the user's hand without having to move the forearm off the armrest of their chair.
  • All mouse users should take a 3-5 minute microbreak per hour from their computer to help break up cumulative stress from continuous usage of the mouse.
  • The user should cradle the mouse in the palm of their hand, and should avoid gripping it. Doing so will reduce muscular stress in the tendons of the forearm muscles.


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