office desk seating - ergonomics

7/29/2019 Office Desk Seating - Ergonomics

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Managing Preventable I njur ies

I n the Off ice Environment

ERGONOMICS in the Office

Environment


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ErgonomicsFrom the GreekErgo(Work)andNomos(Law)

Means fitting the work andthe worker together so that

both are well matched to oneanother.


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Fictional Computer Villains

Plot to take over the world

Enslave people to serve machines

Passionlessly terminate opponents

See and Know everything


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Real Computer Villains

Create physical, emotional and mental pain gradually

Enslave users through promised (though never realized)

productivity

Easily loose critical information


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The Worker

The average office worker

rarely receives instruction how

to properly set up her area for

comfort and efficiency

Normally she has arranged her

area by trial and error

Or she has left it very closeto the arrangement of the

person who just clocked out

(Who also never adjusted it)


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Sitting Posture

Good Seating is

foundational to overall

good office workerposture and position.

Trunk upright or

slightly reclining

(10 degrees or less)

Back rest adjusted to

provide good lumbar

support

One fist width (3-3 1/2)

knee to chair edge

Seated


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Rule of 90s

Knees hips and ankles at

90 degrees or slightly less

Elbows at 90 degrees

or slightly less with a

neutral shoulder

Seated


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Neutral Neck

Dynamic rotation of the

head should be limited to

30 degrees side to side

Neck should be neutral toslightly forward flexed

Neck should never be heldin extension while working

Static rotation of the headto face the monitor orwork is not acceptable

Seated or

Standing


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Look familiar?

This posture should be

corrected with a headset or

use of a speaker phone.


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Twisting and Bending

Seats should pivot, notbacks or hips

May be a clue the space istoo restricted

May indicate flaws inworkstation setup or work

flowMay relate to bad habitsand require education ofstaff


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Static Working Postures

Static loading causes ananaerobic condition inskeletal muscle.

Sustained hold of limbs orobjects against gravity orresistance creates restingtension.

Symptoms of fatigue,

stiffness and pain resultfrom doing little ornothing at all.

Workers should vary tasks

at least every two hours.


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Interface Pressures

32mm of mercury is

sufficient to cut off

capillary blood flow

Nerve is unforgiving of

sustained pressures in

every case


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Reach and Excursion

How far is too far toreach when seated?


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Optimum Working Distance

30 wide x 17 forward reach

10

Horizontal Arc of Grasp

1217 2226 20

39

63

Comfort Zone


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032

inches

63

inches As as general rule

forward reach should

be limited to 2/3 of

maximum for routine

seated work

Maximum vs. Comfortable Reach


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Appropriate Breaks

Breaks are not always rest periods

Balance work activities with worker biorhythms

Change position and tasks at least every two hours

Tasks must use different muscle groups and vary

requirements for posture, pinch and grip


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The Workstation

Ideal VS Reality


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Maximum Adjustability

Since workers vary in shape, size, gender and

stature the workstation needs to be flexible


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The Worker and Workstation

should fit one another


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Desk Height

30-33 inches for writing desk

23-29 inches for keyboarding*

?

* An add on adjustable keyboard tray

may often be used to correct desk height

Sitting


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Establish right to left work flow

The workstation shouldaccommodate logicalflow of work and be able

to contain all routinelyused items withoutextended reach.

As a rule, when usingthings infrequently, getup and take a breakfrom the workstation toretrieve them.


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Proper Mouse Placement

The mouse should always be

positioned on the same level and as

close to the keyboard as possible

(NOT ALONE ON THE DESKTOP!)

It should never require extended

reach or contact with the edge of

any surface

It is often necessary to add an

additional mousing surface to

keyboard drawers or trays.


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Keyboards

In most cases keyboards

should be flat or declined

not inclined to achieveneutral wrist flexion

Never use split or folded

keyboards with typists that

need to look at the keysWrist rests are not

recommended

Inclined keyboards are a

throwback to typewriters


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Monitor

Monitor distance should be a

minimum of 20 inches (no more

than 30)

Brightness needs to be about 10x

greater than a sheet of paper held

to the screen.

Position so that no light source

reflects from its surface when itis off

Flat screens provide a much

smaller footprint


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Bad isnt Always Bad :

If a workstation is rarely used throughoutthe workday (less than 2 hours total)

and/or the worker is at the keyboard for a

few minutes at a time and constantly

changing position an ergonomically awful

setup may be fine for the present.

A brief disclaimer:


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Stretches

Stretches and deskexercises are controversial

Theory: Unused musclegets a chance to lengthenand rest, blood flow isincreased.

Why not take a walk downthe hall, file reports or doother productive tasksinstead?

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