ergonomic work design

8/8/2019 Ergonomic Work Design

1/39

Ergonomic Work Design


2/39

Learning Objectives

Identify ergonomic risk factors in theworkplace

Discuss workplace design issues

Coping with the possible adverse effects of

shiftwork

Evaluate existing workspaces and addresscrucial ergonomic work design issues


3/39

Ergonomic Risk Factors

Awkward PosturesForceful Exertion

Repetitive MotionVibration

Contact Stress


4/39

Awkward Postures

Maintaining good

postures, such as straight

wrists, elbows close to thebody and head straight

and in-line with the torso

is often difficult


5/39

Awkward Postures

Often results toCumulative Trauma

Disorders or CTDs

A properly adjusted

workstation can help

minimize awkwardpostures


6/39

Forceful Exertion

Force is usuallyassociated with

strenuous physical

exertion

Office work seldom

requires this type ofstrenuous exertion

Can result in injuries


7/39

Repetitive Motion

Same motions repeatedly ata fast pace and with littlevariation

Combined with forcefulexertions and awkward

postures results in muscle

strain and other injuries Even the best designed

workstation can not eliminate

all highly repetitive motions


8/39

Repetitive Motion

Effects of repetitive motion maybe reduced bythe following

Task Rotation or Job Enlargement Let

employees do tasks other than their core

tasks

Micro Breaks or Rest Pauses - Buildshort micro pauses into computer use

sessions


9/39

Vibration

Vibration exposure from

prolonged use of power tools

Destruction of nerves

"Raynauds syndrome" or

white finger

Hand Arm Vibration Syndrome

(HAVS)Can be reduced by using

gloves


10/39

Contact Stress

Can occur either internally or

externally Internal stress occurs when a

tendon, nerve, or blood vessel

is stretched or bent around abone or tendon

External contact stress occurs

when part of your body rubsagainst a component of theworkstation, such as the chairseat pan or edge of the desk


11/39

Ergonomic Work Design Issues

Workspace layoutWork surfaces

Standing and walking surfaces

Seating

Storage

Work fixtures

Work environment


12/39

Factors which influence stress

Sitting vs. Standing

Stationary vs. Mobile

Large/Small demand for Strength/Power

Superior/Inferior Horizontal Work Area

Superior/Inferior Vertical Work Area

Length of the Work Cycle Surface Stresses


13/39

Seven types of work

Standing Work

Standing Heavy Lifting/Carrying Work

Seated Repetitive Work with Light Parts

Seated Work With Larger Parts

Seated Control Work

Work with Hands Above Chest

Work With Hand Tools


14/39

Standing Operator

Standing is suitable if very large forces mustbe exerted with the hands or a fairly largework area needs to be covered

Standing in place should be imposed only fora limited period.

The optimal height of the work surface varies

with the type of task performed Twisting, bending and over-reaching should

be avoided


15/39


16/39

Work Surface Heights As a general rule, the strongest hand forces

and most useful mobility are between elbowand hip heights. Thus, the height of theworkstation is determined by the working

height of the hands and the size of the objectworked on

The main reference point is the elbow height

of the operatorWriting and light assembly 107 cm

Tasks requiring large downward - 91 cm

or side forces


17/39

Walking and Standing Surface

Surfaces on which people stand for longperiods should be designed to prevent slippingor falling

Surfaces should provide adequate traction andcomfort

The floor should be flat and free from

obstacles Elastic mats and soft shoe soles can reduce

foot, leg, and back discomfort


18/39

Semi-sitting

Stools may allow the operator to assume a

somewhat supported posture between sittingand standing

Such semi-seats usually do not have full

backrests and do not support the body fully

Although better than standing in place, semi-

sitting is by no means satisfactory becausemuch weight still remains on the feet.


19/39

Sitting Operator

Sitting is suitable for:Tasks that require fine control

Close visual work

When large forces are notrequired

When all items are reachablefrom the seated position


20/39

Sitting Operator

Allows better-controlled hand

movements, but coverage is of a

smaller area

Suitably seated, a person canoperate with their feet and can

apply much force

Free space is required by the legsand feet


21/39

Working Height

Working surface should be at elbow heightwith the upper arm hanging

It has been customary to provide chairs that

are about the popliteal height of the sittingperson Seat height range from about 35-50 cm

Provide suitable height, width, breadth andshape for the pan and backrest


22/39


23/39

Seating

Be easily adjustable whileseated

Have swivel seats for mosttasks

Isolate workers fromwhole-body vibration

Have adjustable armsupport when appropriate


24/39

Foot Operation

Compared to hand movements

over the same distance, footmotions:Consume more energy

Are less accurateAre slower

But are more powerful

Operation of foot controls ismuch easier for a seatedoperator


25/39

Designing Foot Controls

Require repeated operation only from a

seated operatorDesign for pushing roughly in the direction of

the lower leg

Have the person exert small forces by tiltingthe foot about the ankle

Have the person exert large forces bypushing the whole leg, preferably with a solidback support from the seat

Do not require

fine control, continuousoperation, or quick movements


26/39

Types of Hand Use

Fine manipulation of objects with littledisplacement or force

Hand writing, assembly of small parts, adjusting

controls Fast movements toward an object, requiring

moderate accuracy to reach the target, but a

small exertion of force Moving a switch and then operating it


27/39

Types of Hand Use

Frequent movements between targets,

usually with some accuracy, but little forceAssembly task wherein parts are taken

from bins and assembled

Forceful activities with little or moderatedisplacement

Turning a hand tool against resistance

Forceful activities with largedisplacements

Using a hammer


28/39


29/39

Designing for Hand Use

Of the hand digits, thethumb is the strongest

and the little finger the

weakestGripping and grasping

strengths of the whole

hand are larger thanexerted with any digit

alone


30/39

Designing Hand Tools

Push or pull in the direction of theforearm, with the handle directly in

front of it: keep the wrist straight

Provide good coupling between

hand and handle by shape and

friction

Avoid pressure spots and pinch

points


31/39

Designing Hand Tools

Round edges and padsurfaces

Avoid tools that transmit

vibration to the handDo not operate tools

frequently and forcefully by

hand; a robot or othermachine is better suited for

such activities


32/39

Work Fixtures

Operators should not have touse their hands or bodies as avise to hold objects.Mechanical devices do thismuch better

Tooling fixtures and jigs

should be set up to avoidawkward postures andexcessive forces


33/39

Workspace Layout

Work space layout and arrangement shouldallow:

Adjustability to fit each workers size

Worker to maintain neutral posture and avoidawkward or extended reaches and jerky

movements

A variety of working positions to avoid staticpostures


34/39

Workspace Layout

Full range of motion andadequate leg room

Adequate space for and

access to all necessarytools and equipment

Frequently used work times

within easy arm's reach

Unobscured line of sight


35/39

Storage

Storage areas should be organized sothat the workers maintain good body

positions, reduce muscular forces and

avoid excessive reach.Store heavy items between knee and

shoulder height and frequently used

items closest to the operator.


36/39

Shiftwork

Covers a wide variety of work

schedules and implies that shifts

rotate or change according to a set

schedule

Shifts can be either continuous,

running 24 hours per day, 7 days per

week, or semi-continuous, running 2

or 3 shifts per day with or withoutweekends.


37/39

Shiftwork

Often blamed for human

error in nuclear power plant

and airplane accidents,

among othersCommon in essential services

such as hospitals, police,transportation and lately, in

the BPO industry


38/39

Adverse Effects of Shiftwork

Upset one's circadian rhythm

(24-hour body cycle)

Cause sleep deprivation and

disorders of the gastrointestinal

and cardiovascular systems

Make existing disorders worse

Disrupt family and social life


39/39

Coping With Shiftwork

Best solution: Eliminate it!

Other solutions:

The organizational level- primarily

through the design of shift schedules,

education and better facilities The individual level- helping workers to

get better sleep, a healthier diet, and the

reduction of stress

ergonomic work design

Documents