DESIGNING A TRULY ERGONOMIC WORK STATION

2. The keyboard and mouse.

The thought of carpal tunnel syndrome (CTS) strikes fear into the hearts of most office workers, and for good reason. The statistics surrounding CTS are astonishing. In 1996, CTS cases resulted in the highest median number of days away from work for any injury or illnesses--25, compared to five days for all other injuries and illnesses combined. CTS is a painful and debilitating disorder that can take months and even years to heal. However, it can be avoided in most cases with some basic preventative measures.

Get the keyboard off the desk. Recent research shows that the keyboard should be angled away from the user and placed below desk level, so the user's wrists remain straight and the elbows open up to a greater-than-90-degree angle. The best way to achieve this position is with the use of an articulating keyboard holder with negative tilt adjustability. A 1995 Cornell study found that using a lowered keyboard holder on a preset tilt away from the user can help prevent carpal tunnel syndrome. This keyboard position also encourages a healthier seated posture. In addition, the palm support should only be used as a resting place for the palms between periods of typing. It should never, ever support the wrists during periods of typing.

	Typical seated posture while keying; abducted shoulders, forward head, extended wrists, maximum disc pressure on spine.   A negative slope keyboard in a lowered position keeps wrists straight (neutral posture), opens up elbow angles and hip angles, keeps shoulders neutral and encourages recline, which reduces stress on the spine.

Movement is critical-II. As with seated postures, the ability to change positions frequently and easily is the foundation upon which a good ergonomics program is based. A keyboard platform should allow the user to easily change keyboard height and depth as different tasks necessitate.

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Keep the mouse within the Neutral Reach Zone. With the phenomenal increase in graphics applications and Internet use, mousing has become a major cause of CTS. To combat these dangers, it is important to always mouse within the Neutral Reach Zone. Avoiding extreme postures minimizes the possibility of shoulder abduction and wrist flexion/extension.

	Neutral body posture is achieved when working with the Neutral Reach Zone, which is the "area that can be conveniently reached with a sweep of the forearm while the upper arm hangs in a natural position at the side." (Sanders & McCormick, 1993)

Beware the bite of the mouse. In addition to position, the mouse itself also can be a major risk factor. Cornell University research suggests that a larger mouse can reduce wrist extension and CTS risks. Users should monitor their mousing hand and immediately begin mousing with their other hand at the first sign of any pain or tingling. Ideally, the mouse should be symmetrical so it can be used easily in both hands. Likewise, the keyboard platform should allow for mousing on both sides of the keyboard.

	1 3 2 4   5 6 Examples of poor mousing techniques: (1) Extension, (2) flexion, (3) radial deviation, and (4) ulnar deviation impose abnormal forces on the tendinous structures of the wrist, which can lead to fatigue, pain and injury.   Sustainable mousing posture: Ideally, the wrist should be in a neutral position (5,6), decreasing the stress on the wrist's tendon structures.

Click here for information on Humanscale's mousing solutions.