The study of computer ergonomics tells us that the objects that we use most often should be located closest to your body and accessed easily, without awkward body positions or movements. Repeated reaching or prolonged fixed postures that involve leaning forward from your chair are stressful and fatiguing.
Computer Ergonomics Reduce Fatigue
Some people are aware of computer ergonomics and have purchased various ergonomic devices. These devices, such as keyboard trays, gel mouse pads, and ergonomic keyboards rarely provide solutions to the big picture of computer ergonomics. These items must work with each other in order to produce a significant reduction in postural stress. For example, an ergonomic mouse is of little use if it is positioned in an area that requires reaching and stretching in order to operate it. Limiting reaching and stretching for desk items is essential to maintaining a healthy computer ergonomics environment.
The most frequent complaint that I have seen in my office is due to computer work is the combination of mousing and reaching to the desk for the mouse.
Most computer stations are designed in a way that involves the worker operating the computer mouse on a pad on the desk, which is not proper computer ergonomics. Reaching to the desk for the mouse places direct stress on the joints and soft tissues of the neck, shoulder, elbow, wrist and hand.
So how does reaching for the mouse set the stage for injury?
Reaching for the mouse causes you to lean forward in your chair, extend your arm and support the weight of your body through your extended arm.
The stresses placed on the human frame when reaching for the mouse are easily identified. Contrary to popular belief, sitting, which most people believe is relaxing, is hard on the back and don’t support healthy computer ergonomics.
In recent years, studies on postural stress have indicated that we should be sitting upright with our hips flexed at 90 degrees. As it turns out, the most up to date studies show that a slightly reclined sitting posture with the hips flexed at 100 to 115 degrees is ideal if you have to sit at a desk. If your mouse is not positioned close enough to your body, you will have to reach for it. Reaching for your mouse stresses your back by reducing the angle of your hips.
Next, we have to look at the effects of reaching on the neck and shoulder. When the mouse is being operated at a distance that makes the operator reach, the shoulder extends forward and the shoulder blade abducts (rotates forward). This position stretches the muscle groups that connect the medial portion of your shoulder blade to your spine and the superior portion of your shoulder blade to your neck. In the short term, this stretch aggravates the affected muscle groups causing spasm, fatigue, headaches and stiffness in the neck and shoulder. In the long term, this position creates a condition called a “stretch weakness” resulting in muscular imbalance, trigger points and chronic variations of the conditions listed in the prior sentence.
Lastly, placing the mouse too far away, too low, or too much on one side can cause shoulder, wrist, elbow, and forearm discomfort. When the operator is forced to reach for the mouse, his / her body weight shifts forward and ultimately results in weight bearing stress on the extended arm. Spending prolonged periods of time leaning on an extended arm is an unnatural and destructive posture that will eventually lead to the development of a repetitive stress syndrome; likely resulting disorders would include tendonitis of the wrist, elbow or shoulder.