Select the Right Pointing Device, Placement to Reduce Mouse-Related Pain
A pointing device, such as a mouse, can come in many sizes, shapes and configurations. In addition to the conventional mouse, there are trackballs, touch pads, fingertip joysticks and pucks. Selecting the right pointing tool and its placement is an important factor in creating a safe computer workstation.
According to the Occupational Safety and Health Administration, many injuries can arise from incorrect placement or selection of a pointing device. For instance, if the pointer is not near the keyboard, it may force an employee to work in awkward positions, or require the worker to use forceful or stressful hand exertions while using the device. Over prolonged periods of time, these exertions can place stress on the shoulder and arm and increase the likelihood that the employee will also assume awkward wrist and shoulder postures, which could then lead to musculoskeletal disorders.
However, you can reduce these risks by using a pointer/mouse that allows the worker to maintain a straight, neutral wrist posture. This may involve adjustments in the employee's chair or desk keyboard tray. If the keyboard tray/surface is not large enough to accommodate both the keyboard and mouse, employers should:
- Use a mouse platform positioned over the keyboard. This design allows the mouse to be used above the number key pad.
- Install a mouse tray next to the keyboard tray.
- Use a keyboard that has a pointing device, such as a touch pad, incorporated into it, or chose a keyboard without a number key pad, which leaves more room for the pointer/mouse.
- Use a mouse pad with a wrist/palm rest to promote neutral wrist posture.
- Substitute keystrokes for mousing tasks. These strokes include Ctrl+S to save and Ctrl+P to print.
Examine size, shape of devices. The inappropriate size and shape of pointers can increase stress, cause awkward postures, and lead to overexertion. For example, using a pointing device that is too big or too small may cause you to increase finger force and bend your wrist into awkward positions. Using the left hand to operate a device that is designed for right-hand use can also create force and posture issues and may create contact stress to the soft tissue areas in the palm of the hand. Contact stress can create irritation and inflammation.
To select the proper device, ensure that it is:
- Appropriately sized and requires minimal force to generate movement. For example, a puck device must be small enough for single-handed operation (generally,
1 1/2 to 2 1/2 inches wide, 2 1/2 to 4 1/2 inches long, and 1 to 1 1/2 inches high).
- Reduce the strain on hands by reducing pointing device use. Using keyboard functions, such as page down, may reduce mouse use and provide rest for hand and arm muscles.
- Use another type of device that fits the hand better or doesn't require bending the wrist while gripping. A fingertip joystick, touch pad, or trackball may be less fatiguing for certain tasks.
Don't neglect sensitivity of device. Another potential hazard is ensuring the sensitivity for the input device is appropriately set. If a pointer has the wrong setting, it could require excessive force and awkward hand postures to control its movement. For example, a mouse that is too sensitive may require excessive and prolonged finger force to provide adequate control. But a mouse that has insufficient sensitivity may require large deviation of the wrist to move the pointer around the screen. Exerting prolonged force or repeatedly bending the wrist can fatigue the muscles of the hand and increase the risk of musculoskeletal injuries.
However, these hazards can be mitigated by making sure:
- The sensitivity and speed (how fast the pointer moves on the screen when the pointing device is moved by the hand) is comfortable and adjustable. The pointer should be able to cover the full screen while the wrist is maintained in a straight, neutral posture.
- The sensitivity is set to allow the employee to control the pointing device with a light touch. Most current devices have sensitivity settings that can be adjusted through the computer control panel.
- The employee refrains from tightly gripping the mouse or pointing device to maintain control.
- The trackball's exposed surface area is at least 100 degrees. It should feel comfortable and rotate in all directions to generate any combination of movement.
Teach employees proper technique. In addition, employees should be sure that they are using proper technique when using their mouse. Workers need to think of their hand, wrist and forearm as one body part, and need to be sure that the wrist and hand are moved with the forearm, not on their own when repetitive movements can lead to injuries.
For proper mousing technique, employees need to:
- Avoid twisting the wrist while working. Keep the wrist in a stationary position and allow the arm to do the work.
- Relax the hand guiding the mouse -- avoid using a firm grip -- and relax the fingers as well. Don't hold fingers on top of the mouse when using the mouse, and release the mouse when not using it.
- Pay attention to the thumb. Keep it relaxed and avoid using it excessively with a pointing device such as a trackball.
- Consider changing it up. If an employee's job requires a large amount of point-and-click work, encourage workers to change hands (assuming the device is compatible for both hands). It may slow down work until the worker adjusts to using the other hand, but it could prevent an injury.
January 19, 2009
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