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Fitting the Human: Introduction to Ergonomics. Dr. Katie Cahill Science 295. The History of Ergonomics. Foundations of ergonomic science observed in Ancient Greece - Hippocrates - Egyptian Dynasties Term coined during World War II by Hywel Murell Continued with the space age - PowerPoint PPT Presentation
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The History of ErgonomicsFoundations of ergonomic science observed
in Ancient Greece- Hippocrates- Egyptian Dynasties
Term coined during World War II by Hywel Murell
Continued with the space ageFurther developed during the information
age
What is Ergonomics?AKA Human FactorsDerived from Greek words ergon (work) and
nomos (law)According to the IEA, ergonomics is the
scientific discipline concerned with understanding of interactions among humans and other elements of the system, and the profession that applies theory, principles, data and methods to design, in order to optimize human well being and overall system performance.
What is Ergonomics?Main focus is the safety of the personFactors:
Body posture and movement• Environmental factors• Work Organization
Interdisciplinary approach - biomechanics, physiology, psychology, mechanical engineering, industrial design, information technology and management
So what?Social Value
Human well being, safety, health and comfortReduces accidents at work, at home, etc. by
reducing human errorImproves relationship between operators and
equipmentDecreases absence from work
Diseases of musculoskeletal system (LBP) Psychological illnesses (stress)
User friendly products
So what?Economic Value
Reduction of costs by preventing work related problems
Health care costs for treatmentCosts associated with loss of laborCompanies can improve efficiency, worker
productivity and cost reductionErgonomically designed products deliver
benefits to customers and edge out competition Special situations – short vs. tall, overweight,
handicapped, elderly, pregnant women
Section I: The Human BodyAll humans have similar bodiesBodies of people evolve to meet special circumstances
Unique climates, special diets, athletic trainingDifferences in bodies within the species of mankindRecognize these differences to accommodate
individualityThe following chapters address these differences:
Chapter 1 Body SizesChapter 2MobilityChapter 3 Muscular WorkChapter 4 Body strength and load handling
Body SizesBody sizes differ
Growth cycle: quick growth during childhood, consistency for 20 – 40 years, degenerative changes
Men are normally taller than womenTaller and shorter individualsDiffering body proportions
The Earth’s PopulationsBodies of populations described in height and
weight Table 1.1 Average stature of 20 regionsAnthropometrics – study of the size and
proportion of the bodyWhy is it important to know the variances in
body stature?
How to measureMay need more specific measurements than
just height and weightTraditional method – taking measurements
with hand held devicesEmerging technique records 3D dimensions
of the human bodyFigure 1.1 = most common measurements
takenTable 1.3 use of the measurementsData is missing from many populations due to
its laborious and expensive nature
No “Average Person”Problems with average data
Can’t base designs of the average because too small for some and too large for others
Need to take into account the extremesNeed to understand the “normal” distribution
Statistically analyze a distribution curve“bell cure” or Gaussian curveMajority cluster in the middle and outliers on
either end represent extremes
Average and Standard DeviationAverage is the measure of the middle or
expected value of a data setThe standard deviation is a statistic that tells
you how tightly all the various examples are clustered around the mean in a set of data
With tightly bunched data, the bell-shaped curve is steep, the standard deviation is small
With spread apart data, the bell curve is relatively flat, the standard deviation is large
Smaller SD = more reliable data
PercentilesNumerical value of a specific point in a
distribution calculated from the mean and the standard deviation
The mean is normally in the fiftieth percentile range; half the data lies above and half below
Fifth percentile is of design interest: <5% and >95%
p5 is 1.65 SD below the mean and p95 is 1.65 SD above the mean
Table 1.6 Values necessary to calculate percentage points
Hand Size DataFigure 1.3 and Table 1.7Hand measures
LengthBreadth of knucklesMaximal breadthCircumference at knucklesWrist Circumference
Designing to Fit the BodyEven among seemingly similar groups, body
sizes and segments differEx 1 US agriculture workers are shorter by an
average of 2.5 cm than other workersEx 2 Female American agriculture workers
have larger waist circumferences than other occupations
Ex 3Protective Service workers are taller and heavier
Design Principles1. Custom fit each individual2. Have several fixed sizes3. Make it adjustable4. Design for the extreme bodies; assures any
individual can: Operate a gadget Fit through any opening Cannot pass through a dangerous opening
5. Select those persons whose bodies fit the existing design
Fit a RangeSolutions 2 and 3 are the most commonAllows us to select a body size range we
intend to accommodateAim to accommodate the central 90%Exclude the top and bottom 5%; total 10%
extreme sizes
Select Design LimitsMinimum and maximum depend on design
purposeSeveral sizes (solution 2)
Ready made clothingAdjustment features within a range (solution 3)
Shoes with lacesOffice chairs
Statics and dynamicsData collected is often in a static positionMovement must be taken into account with
designs (Table 1.8)
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