Your Computer Workstation

Dan MacLeod

www.danmacleod.com

June 10, 2002

Before reading this, make sure you understand the basic principles of ergonomics on which this is based.  It is much more important for you to learn the underlying principles rather than the details of current prescriptions to problems with office ergonomics:

  • Your work station may be different from those referred to in the typical list of tips and suggestions.  Understanding the principles will help you sort how what applies and how it applies to you. 

  • By learning the principles you will understand how to evaluate changes in technology and new products that will appear.
  • The principles will help you to evaluate any task, whether at home or in general industry, not just that of the computer workstation.

The following illustration provides a good overall summary.  Please note the differences between the principles that are required (left hand list) versus the tips (right hand list) that may may have exceptions depending upon the circumstances.

Principles
(Required for sustained work)

Neutral Posture:

- neck aligned
- shoulders relaxed
- elbows at side
- curve in back
- wrists in neutral

No pressure points on chair

Knee clearance

 

Movement and change (see below)

overall summary

Tips
(Exceptions may be possible)

Top of screen at about eye level

Screen straight ahead

Copyholder

Keyboard at about elbow height

Wrist rest

 

Footrest (if needed)

 

Note!

There is no one posture that is "correct" for an eight-hour day — the body needs change and movement. The point is to (a) have a good starting position from which you can vary, and (b) avoid having the furniture force you into a single, contorted posture.

move, change and adjust

 

Comments

Contoured Keyboard
These unconventional keyboards help place the wrists in their neutral postures.  Other adjustable keyboards are on the market and may be helpful in some circumstances.  However, the design shown at right costs no more than the traditional keyboard.

My prediction is that in a few years these new keyboards will be standard and the traditional straight keyboards will look as old-fashioned as a black-and-white television set.

contoured keyboard

Touchpads
Touchpads have a number of advantages over mice:
  • eliminate static gripping of the mouse (related to wrist disorders)
  • motions are limited to the index finger, which moves easily
  • reduce reaching, in that they take up less desk space than do mice
  • can be integrated into the keyboard

My prediction: The days of the mouse are numbered.

touchpad

Note: For extremely heavy users there may not be any one single input device that eliminates all discomfort.  Using combinations of devices and alternating between left and right hands might be required to eliminate any one static hand posture.

Tilted Keyboards
Your forearms and keyboard do not necessarily need to be parallel to the ground (and your elbows at right angles).  You may wish to tilt your keyboard back when you lean back, or tilt it forward when you are working up close.

The key is to have the wrists in neutral, the shoulders relaxed, and your elbows at your side.

keyboard, tilt up
keyboard, tilt down

Chairs
If you shop wisely, you can get excellent chairs for modest prices.  Even chairs sold in the office warehouses have a remarkable set of ergonomic features at low prices and may be sufficiently durable for some applications such as home use.

Basic Features:

  • adjustable height

  • backrest adjustable up and down, with good lumbar support
  • backrest moves forward and backward, with locking mechanism
  • adjustable armrests (see below)

Ideal Features:

  • tiltable seat pan

  • rocking mechanism with lock

Chair

Arm Rests
There used to be quite a debate on whether task chairs should have arm rests or not.  With the advent of inexpensive adjustable arms, now they are a basic feature.  Many chairs can be retrofitted, so you don't need to buy a whole new chair.

Put them at elbow height to eliminate the static load on your shoulders.

armrest

Sitting Posture
There's an old rule of thumb that suggests you sit at 90 - 90 - 90, that is, with ninety degree angles at your hip, elbows, and knees.  However, there's no science behind that rule. Apparently, someone a long time ago made the rule up because it looked like it ought to be correct.

The studies actually say a semi-crouch (with good lumber support) is better.

My own view is not that the right-angled posture is "bad."  It's an easy rule to remember and it can help you get in a good starting point from which you can adjust.

But it certainly is OK to lean back as you work, as long as you "keep the curves" and have good lumbar support.

And once again, you should change positions frequently anyway.

c lean back.jpg (47068 bytes)

Typing Repetitive Motions

Many studies have shown a relationship between hand/arm disorders and time at the keyboard, sometimes giving the impression that keyboard work should be restricted.   However, it seems that that if all the issues of posture and static load are taken care of, there may be no need to limit the amount of time at a keyboard. 

typing

For additional information see Dan's Books and Training Materials.