Re-evaluating the Desktop: A Different Approach to Using the Mouse

There are many good reasons why some users choose to incorporate keyboard trays and arms into their workstation. The primary reason is to attain the ideal height at which to use the keyboard and mouse. However, not all mice will work optimally in such a setup, and there are a few mice that have been designed with the intent of being used on a desktop and may not work for everyone on a typical keyboard tray. This month we will discuss a few of these mice and explain the reasons behind such a design.

Some researchers in ergonomics are of the opinion that the hand should be as relaxed as possible during both active and inactive periods of using the mouse. The basic idea is that the hand should retain its natural positioning as much as possible, and this involves preventing the hand from gripping the mouse (fingers should be slightly bent with the thumb opposed), while keeping the forearm from 'hovering' above the work surface. Although the height of one's workstation is important, it is claimed that one really needs to adjust the desk itself (or one's chair) instead of altering one's workstation configuration to accommodate this need. The appropriate height for the desk and chair would have the user's forearm resting on the desk at 90 ° from the elbows (illustration A) and at up to 45° from a vertical axis (illustration B), so that both hand and forearm are optimally at rest. Only then can a mouse be used safely over the long term.

The science behind this idea is actually quite simple: since we know the positions the hand and arm naturally conform to when relaxed, a mouse which is designed to help maintain these positions would seem to be optimal. This 'relaxed' positioning of the hand and forearm should meet these basic conditions:

1. The thumb should be opposed to the fingers, so that precision movement can be obtained during usage but relaxation can be optimized when the mouse is not in use.

2. The hand should be in a slightly supinated position of about 15° - 25°.

3. Hand, wrist and forearm should be fully supported on the desktop to remain in full muscular equilibrium, also known as 'passive adaptation'. This totally relaxing stance allows the hand to maintain its 'position of function'.

Examples of mice that have been designed according to these strictures include the OrthoMouse from Orthovia and the HandshoeMouse from Hippus (see right photo). Both mice are meant to be used on the desktop, since it is important that the forearm be supported so that all relevant muscles used in operating one's mouse are sufficiently relaxed and free of undue stresses (such as 'hovering' above the mouse or worksurface).

The main problem with traditional mice, and even some 'ergonomic' mice, is that they require or force the fingers to overwork the extensor muscles, while keeping the hand in a pronated position (palm down) or in excessive supination (palm directly vertical). There is also the problem of wrist extension if the hand bends at the wrist (i.e. moving laterally) while the hand and wrist are in a fully vertical (i.e. unpronated) position (see left photo). All these additional stresses to the hand, wrist and forearm can lead to painful injuries and are a direct result of insufficient relaxation of all the muscles involved in using the mouse. This is why sufficient desktop space is so important, since it is the primary means of keeping one's hand, wrist and forearm fully supported and relaxed at all times.