The Key to Keyboarding

Office Ergonomics October 18, 2012

If you find 10 references to keyboard use on the Internet these days, you will likely find 10 different bits of instruction for keyboard use and placement.  Who do you believe?

Rather than pointing to who is “more” correct or “less” correct, let’s take a practical approach and you can decide for yourself.  Back in the dark ages of ergonomics, we insisted on the 90-90-90 rule of 90 degrees of hip, knee and elbow flexion.  Current research and a bit-o-common-sense has shown that this thinking is out date, especially with new accessories and furniture design that better accommodates the shapes and sizes of end users.

Keyboards, which were once only available in flat rectangular shapes, are now available in waves and gables, with/without attached 10-key pads, with standard keys that provide tactile/audio feedback, keys on film without tactile feedback but with audio (optional) and projection with no feedback.  The keyboard can have full-sized or compressed (smaller) keys.  And some even allow programmable keys for macro functions or a switch between QWERTY and DVORAK layout.

The “key” to good keying is fitting the size/shape the to user and matching the sensory feedback to the needs of the user.  If you have narrow shoulders, then a standard keyboard might work fine for you.  However if you have broad shoulders, then perhaps a split or wave keyboard that separates the left and right sides with an outward angle may be your best bet.  Studies show that the gable or upward peak in from the center is better for reducing intercarpal pressure, however if you take frequent breaks, maintain neutral wrist posture and use the keyboard for short duration, then this feature becomes less important.  Most people can transition easily with less than a 20-30 degree gable (peak). Beyond this the incidence of keying error increases.  Best bet is to adjust the keyboard to fit your body size.  And select a sensory feedback system that minimizes keying error.  If you have small fingers, you may be able to adapt to a compressed keyboard, however broad fingers do better on a full size keyboard simply due to the match between the finger and the key.

In terms of distance forward of your body, keeping the keyboard toward the leading edge of the support surface minimizes reach and keeps your elbows closer to your body in a more neutral shoulder angle.  HFES/ANSI suggests leaving a 4” space between the keyboard and leading edge of the desk for a palm rest (to be used when thinking, not data entry).  For people with very little “luggage” up front, the keyboard might be close enough that your elbows are directly under your shoulders at 90 degrees of elbow flexion. But for the majority of people, simple body shape and mass will require the elbows to be slightly forward.  Generally anywhere between 2”-3” forward of the center of the rib cage is acceptable.  Beyond this requires extra effort from the muscles on top of the shoulders.  Keeping the elbows close to the body improves the option of using armrests for support during data entry which reduces muscle activity in the area on top of your shoulders and encourages use of the upper and lower backrest to stabilize your shoulder blades on your trunk.  Studies show that even resting your entire forearm on the desk (with excessive shoulder flexion) vs. armrest increases muscle activities in the muscles on top of your shoulders. 

In terms of horizontal location, if you primarily use the alphanumeric keys, then center the G/H keys with the center of your body to prevent reaching across your chest.  If you need to use the 10-key pad, then shift the keyboard to left for this duration so it is centered to your right hand.  Or select a keyboard with a detachable 10-key pad that can be placed as needed.

Finally in terms of height on the work surface, after adjusting the chair height to fit you, adjust the work surface so that your wrists are relatively straight.  A little bending upward or downward is acceptable but only by a few degrees.  Straight is better.  Let the thickness/gable of your keyboard determine how far below your palms that you should set the height of the keyboard support. 

With the wide variety of equipment choices these days, rather than put a “number” on distance and joint angles, look at the end user.  If you are in neutral postures, then chances are you set up is just fine.

– Written by Miriam Joffe, MS, CPE

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