Introduction to Ergonomics-final

7/28/2019 Introduction to Ergonomics-final

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Work Systems and the Methods, Measurement, and Management of Work by Mikell P. Groover, ISBN 0-13-140650-7.

2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

Human Factors Engineeringand Work Design


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WORK METHODS DESIGN


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Work Methods Design/Methods Engineering

Emphasis in Methods EngineeringEfficiencyCost reductionLabor reductionWorkplace layoutFacility layoutElimination of waste

One best way in doing work


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Human Factors Engineering/Ergonomics

Emphasis in Ergonomics and Human FactorsSafetyComfortInteraction between human and equipmentWorkplace environmentFitting the work to the individualReduction of human errors

Accident avoidance


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Industrial Accidents

Human Factors Engineering
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Human Factors

Human factors is synonymous with ergonomicsErgonomics emphasizes work physiology andanthropometry

Europe industrial work systemsHuman factors emphasizes experimentalpsychology and systems engineering

U.S. military work systems


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Human Factors

Physiology - a branch of biology concerned withthe vital processes of living organisms and howtheir constituent tissues and cells function

Important in work because work requires

expenditure of physical energy Anthropometry a branch of anthropologyconcerned with the dimensions of the humanbody, such as height and reach

Important in work because the dimensions of the human body affect capabilities of worker


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Physical and Cognitive Demands

Most work activities require a combination of physical and cognitive exertions


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PHYSICAL DEMANDS


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MENTAL DEMANDS


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What is Ergonomics?

ERGONOMICS

Ergon Nomos(WORK) (LAW)

Study of Human at work

Fitting the task to the worker

(Chaffin and Andersson, 1984)

worker

Job design workplace


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Objectives in Ergonomics

Greater ease of interaction between user andmachine

Avoid errors and mistakesGreater comfort and satisfaction in use of theequipmentReduce stress and fatigueGreater efficiency and productivitySafer operation

Avoid accidents and injuries


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SAMPLE ILLUSTRATION


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Ergonomics Application Areas

Work system designObjectives: safety, accident avoidance,improved functional performance

Also includes environment such as lightingProduct design

Objectives: safety, comfort, user-friendly,mistake proof, avoidance of liability lawsuits


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LIGHTING


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PRODUCT DESIGN


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Ergonomists What They Do

Research on human capabilities and limitationsDiscover the characteristics of humanperformance, e.g., how much can anaverage worker lift?

Design and engineering applicationsUse the research findings to design better tools and work methods


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LIFTING REQUIREMENTS


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Fitting the Person to the Job

Considers workers physical and mental aptitudesin employment decisions

For example, using worker size and strength ascriteria for physical work

Common philosophy prior to ergonomicsFPJ is still important

For example, educational requirements for technical positions


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Fitting the Job to the Person

Opposite of FPJPhilosophy: design the job so that any member of the work force can perform itWhy the FJP philosophy has evolved:

Changes in worker skill requirementsDemographic changes (e.g. more women inthe workforce)

Social and political changes (e.g., equalopportunity laws)


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Human-Machine Systems

Basic model in ergonomicsDefined as a combination of humans andequipment interacting to achieve somedesired result

Types of human-machine systems:1. Manual systems2. Mechanical systems3. Automated systems


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System Components

The humanThe equipment

The environment


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Human Components

Human senses - to sense the operationVision, hearing, touch, taste, and smell

Human brain - for information processingThinking, planning, calculating, makingdecisions, solving problems

Human effectors - to take actionFingers, hands, feet, and voice


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Machine Components

The process function or operation performedby human-machine systemDisplays - to observe the process

Direct observation for simple processes Artificial displays for complex processes

Controls - to actuate and regulate the processSteering wheel, computer keyboard


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Environmental Components

Physical environmentLocation and surrounding lighting, noise,temperature, and humidity

Social environmentCo-workers and colleagues at workImmediate supervisorsOrganizational culturePace of work


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Human-Machine Interactions


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Topic Areas in Ergonomics

Physical ergonomicsCognitive ergonomicsThe physical work environmentOccupational safety and health


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Physical Ergonomics

How the human body functions during physicalexertion

Physiology vital processes carried out byliving organisms and how their constituent

tissues and cells functionHow physical dimensions of the body affectcapabilities of worker

Anthropometry physical dimensions of the

human body


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Biochemical Reactions in Metabolism

Food categories:Carbohydrates (4 kcal/g) converted intoglucose (C 6H12 O 6) and glycogen

Primary source of energy muscle

Proteins (4 kcal/g) converted into aminoacids

Lipids (9 kcal/g) converted into fatty acids

(acetic acid and glycerol)


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Energy Expenditure Rates

Sleeping BMR m Standing (not walking) 2.2 kcal/minWalking at 4.5 km/hr 4 kcal/minJogging at 7.2 km/hr 7.5 kcal/minSoldering work (seated) 2.7 kcal/minMowing lawn (push mower) 8.3 kcal/minChopping wood 8 kcal/min

Shoveling in front of furnace 10 kcal/min


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Work Activity and Energy Expenditure

Energy expenditure,heart rate, and

oxygen consumptionfor severalcategories of workactivity


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Muscle Endurance


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Static Dimensions of Human Body

Standing

Seated

d h f l d


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Standing Heights of Males andFemales throughout the World

Males FemalesRegion Centimeters Inches Centimeters InchesNorth America 179 70.5 165 65.0Northern Europe 181 71.3 169 66.5Central Europe 177 69.7 166 65.4Southeastern

Europe

173 68.1 162 63.8

India, North 167 65.7 154 60.6India, South 162 63.8 150 59.1Japan 172 67.7 159 62.6Southeast Asia 163 64.2 153 60.2

Australia

(European)

177 69.7 167 65.7

Africa, North 169 66.5 161 63.4 Africa, West 167 65.7 153 60.2


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Normal Distribution in Anthropometry

Normal distribution for a given anthropometricvariable of interest


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Different Sizes for Different Size Users

Coat sizes 37 38 39 40 42 44 46 48 50 52 54 56 58 60

Short (under 58) x x x x x x

Regular (58 to 511) x x x x x x x x x x x x x x

Long (6 to 63) x x x x x x x x x x x

Extra long (over 63) x x x x x x x x

Portly short (under 58) x x x x

Portly regular (58 to511)

x x x x x x

Example: Mens suit coat sizes available frommail-order clothing store


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Cognitive Ergonomics

Concerned with the capabilities of the humanbrain and sensory system while performinginformation processing activitiesHuman cognitive processes include:

Sensing and perceptionUse of memoryResponse selection and execution


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Anatomy of the Human Eyeball


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Anatomy of the Human Ear


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Physical Work Environment

Visual environmentLighting levels and workplace design

Auditory environmentIntensity and duration of noise

Climate Air temperature, humidity, air movement,and radiation


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Incident Light is at Angle

E = I cos / d 2


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Types of Luminaires

Direct lighting


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Types of Luminaires

Indirect lighting


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Types of Luminaires

Combination of direct and indirect

lighting


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Occupational Safety and Health

Occupational safety concerned with theavoidance of industrial accidentsOne-time events that cause injury or fatality

Occupational Health concerned with avoiding

diseases and disorders caused by exposure tohazardous materials or conditionsDevelop after prolonged periods of exposure

May take years before symptoms reveal theonset of the malady


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Ergonomic related injuries

May be called:CTDs (cumulative trauma disorders)RSIs (repetitive stress injuries) RMIs (repetitive motion injuries) Which are all considered:MSDs (musculoskeletal disorders) MSDs can affect muscles, tendons,nerves, joints and spinal disks.


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Common types of MSDs

TendonitisCarpal Tunnel SyndromeTennis ElbowNeck and Back injuries

Strains/SprainsBursitisThoracic Outlet SyndromeTrigger finger


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Risk factors and causes of MSDs

Task Physical CharacteristicsRepetitionForcePostureContact traumaVelocity/accelerationDurationSegmental VibrationRecovery TimeHeavy Dynamic exertion


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Risk factors and causes of MSDs

Environmental CharacteristicsHeat StressCold StressWhole Body VibrationLightingNoise


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Identifying Risk Factors

Conditions or circumstances that increasethe chances of developing a MSD.The likelihood of developing an injury isdependent on the frequency and duration of exposure to risk factors.Both occupational and personal risk factorscan affect an individuals well being at home

or work.


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Repetition

Occurs when the same or similar movements are performed frequently.Repetition can also occur when differenttasks are performed if those tasks have thesame movements.Injury may result from repetition when thetissues do not have adequate time to

recover.


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Force

Force is the amount of physical effortrequired by a person to do a task or maintain control of tools or equipment.

A pinch grip produces 3-5 times more force

on the tendons in the wrist than a grip withthe whole hand.With excessive force the muscles arecontracting much harder than normal, thiscan lead to stress on the muscles, tendonsand joints.


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Awkward Posture

Is a deviation from the neutral bodyposition.

A neutral body position is safest and mostefficient position in which to work.

Awkward posture puts stress on muscles,tendons and joints.Wrist, shoulder, neck and low back


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Static Posture

Static posture occurs when one position is heldfor a prolonged period of time.The muscles will become fatigued from a lackof blood flow during a static posture.

This fatigue can lead to discomfort and eveninjury.


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Contact Trauma

Local mechanical stress generated fromsustained contact between the body and anexternal object

Local mechanical stress generated from shockimpact


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Velocity/Acceleration

Angular velocity/angular acceleration is the speedof body part motion and the rate of change of speed of body part motion, respectivelyMean wrist flexion/extension of 490 deg/sec in lowrisk jobs and 820 deg/sec in high risk jobs (Marrasand Schoenmarklin, 1991, 1993)


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Duration

Time quantification of exposure to a risk factor,minutes or hours per day or as the years of

exposure to a risk factor or a job


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Recovery Time

Time quantification of rest, performance of lowstress activity, or performance of an activity thatallows a strained body area to rest.Short work pauses have reduced perceiveddiscomfort (Hagberg and Sundelin, 1986)Rest periods between exertions have reducedperformance decrement (Caldwell, 1970)


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Heavy Dynamic Exertion

Muscle demand for metabolites can not be met(metabolic energy expenditure rate exceeds the bodysenergy)Localized fatigue tired/sore musclesWhole body fatigue (from long-term heavycarrying/lifting/climbing stairs)


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What you can do to prevent injury.

Develop an Ergonomics program.Take proper breaks.Health and Fitness.Be aware of your hobbies away from work.


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Adjusting the Workstation

Adjust the Chair.

Adjust reach requirements.

Adjust focal requirements.


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Correct the Environment

Check lighting, noise and temperature.

Check work pace and stress levels.

Check work processes.


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Improve Posture and Habits

Modify wrist/hand motions

Improve neck and back postures

Consider personal preferences


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Personal Protective Equipment

PPE acts as a barrier between a person and ahazard.PPE is only appropriate in situations whenengineering or administrative controls cannotbe implemented.Back belts and other braces are not consideredPPE. These devices should not be used inplace of incorrect work techniques.

Documents

Introduction to Ergonomics-final