Dept. of Biomedical, Industrial, & Human Factors Engineering 1

Workstation Design

Sitting at WorkImproves well-being, efficiency, reduces fatigue

Standing is poor physiologically (static work)

¾ of worker in industrial countries are sedentary

AdvantagesTake weight off legs

Increase stability of upper body posture

Reduce energy consumption

Reduces demands on circulatory system

DisadvantagesSlackening of abdominal muscles

Spine curvature impedes digestion and breathing

Stresses spine and back muscles, increases disc pressure

Dept. of Biomedical, Industrial, & Human Factors Engineering 2

Seat designComfortable chair

Seat pan tilt 24ºBackrest tilt 105-110º to seat panLumbar pad 100-180 mm with apex between 3rd and 5th lumbar vertebrae

Office chairsGeneral recommendation: high back-rest with back contour – better to support weight of trunkSpecific features

Adaptable to traditional and computer workAccommodate forward and reclined seatingAdjustable angle backrestBackrest height 500 mm from seat surfaceBackrest should have well formed lumbar pad from L3 to sacrumSeat pan: 400-450 mm across, 380-420 mm deep, cavity in seat, lightpad, non-slip, permeable materialFootrestsAdjustable height, swivel, rounded front edge, 5 arm base, user-friendly controls

Dept. of Biomedical, Industrial, & Human Factors Engineering 3

Seat designPromote lumbar support

(a) Standing (b) SittingMinimize disc pressure

Discs between vertebrae and spine can be damaged due to excessive pressureUnsupported seating (i.e., no backrest) increased pressure

Minimize static loading of back musclesSlumping will reduce but causes other problems

Reduce postural fixitySitting in one positionReduces blood flow to discsChair design can allow user to rock and reduce problems

Inward arch

Hip

Outward arch

Hip rotates ~60

Dept. of Biomedical, Industrial, & Human Factors Engineering 4

Computer workstations

VDT operator tied to workstationAttention on screen

Hands on keyboard

Problems:Constrained posture

Repetitive activities

Poor photometric display characteristics

Inadequate lighting

DiscomfortsVisual strain

Physical discomfort in back, neck/shoulder, forearm, wrist, hand

Reported problems highest among data-entry and full-time typists

Dept. of Biomedical, Industrial, & Human Factors Engineering 5

Computer workstations

Workstation characteristics linked to discomfortsKeyboard height

Nor forearm/wrist support

Key tops too high above table

Wrist deviation (keyboard design)

Head inclination (visual field placement)

Insufficient leg room

Should provide adjustabilityKeyboard height

Screen height, distance, inclination

Document holder inclination

Dept. of Biomedical, Industrial, & Human Factors Engineering 6

Preferred VDT Workstation Settings

Grandjean et al. (1983)N=68: 48 females, 20 males45 conversational computer work, 17 data entry, 6 word procesing

DeskIf keyboard: 80 mm desk – 630-790 mm 30 mm desk - 680-840 mmOverall: 650-820 mm height

Screen:75 % users positioned between 710-930 mmDepends more on individual preference than anthropometry

PostureTrunk inclination: 100-110 degrees

Only 10 % uprightPreferred slightly open elbows

Dept. of Biomedical, Industrial, & Human Factors Engineering 7

Preferred con’t

PostureArm/wrist support

80% used if available

50% used desk if unavailable

DiscomfortWas reduced by implmenting adjustable workstation with preferred settings

Neck, shoulder, back reduced

Effects of adjustable workstation enhanced by good chairs

Dept. of Biomedical, Industrial, & Human Factors Engineering 8

Guidelines

Furniture as flexible as possibleKeyboard height 700-850 mm

Screen center height 800-1100 mm fro floor

Screen inclination from horizontal 105 degrees

Screen distance to table edge 500-750 mm

If not adjustable, not for continuous use

Adjustable controls should be easy to use

Provide ample knee and foot space

Promote easy body movement but minimize excessive motions

Dept. of Biomedical, Industrial, & Human Factors Engineering 9

Keyboard DesignTraditional design with 4 parallel rows of keys

Unnatural posture of wrists and hands

Mechanical required more force

Modern keyboard activityMore keys

Less force

Greater keying speed

More users

Physical discomfort, tendinitis, tenosynovitis, CTS

Flat keyboard assist resting of forearm and wrist on deskMinimal height

Split keyboards: 2 pairs with 30 degree opening and downward tilt 0-90 degreesLess pain fatigue

Less electrical activity with 10-30 degree tilt downward and split

Large forearm/wrist support

New technologies – voice recognition

Dept. of Biomedical, Industrial, & Human Factors Engineering 10

Carpal Tunnel SyndromeAffected area