Engineering Anthropometry

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Engineering Anthropometry

• IENG 321 Ergonomics and Human Factors
  Engineering
• Spring 2009

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Definition of Anthropometry

• The part of anthropology (study of humans) having
  to do with measurements of the human body to
  determine differences in races, individuals, etc
• Source Websters New 20th Century Dictionary
  (1970)

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Definition of Anthropometry

• Anthropometry is a science that deals with the
  measurement of size, weight, and proportions of
  the human body. It is empirical (experimentally
  derived) in nature and has developed quantitative
  methods to measure various physical dimensions.
  (Chaffin, 1984)

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Historical Perspective

• 13th century Marco Polo noticed different body
  sizes and shapes of new races
• Physical Anthropology traced to him
• Leonardo da Vinci (The Vitruvian Man, 1485)
• Standards start to show in 1906 (Monaco) and 1912
  (Geneva)
• Anthropology branch of US Air Force had dramatic
  impact

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Measurements

• Reference planes
• Taken between solid identifiable bony landmarks
  in standard anatomical positions
• Anthropometric measuring kits
• 3-D body scanning (esp. for functional
  anthropometry)
• Motion capture systems
• Develop regression models with statistical
  relationships

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Reference Planes
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Anatomical Landmarks
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Measurement Postures
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Anthropometric Data Sets

• Normal (Gaussian) Distribution (m, s) (Table 1-2)
• Skewness
• 0 Symmetric
• Left Skew
• - Right Skew
• Kurtosis
• 3 normal distribution
• gt3 peaked (lower s)
• lt3 flat (higher s)
• Correlations (Table 1-3)
• Closely related dimensions with correlation
  coefficient (r) of at least .7 acceptable to base
  design decisions
• Explains 50 of the variance (r2)
• Important in developing regression models (Table
  1-4)

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Anthropometric Data Sets
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Functional Anthropometry

• Static dimensions not always suitable
• Vehicle cockpit design, workstation layouts,
  personal protective equipment and escape hatch
  design
• See Figures 1-12 and 1-13
• Designing for the average
• Typical or default (Restaurant seating)
• Cheapest but least preferred
• ADA accommodations
• Designing for the extremes
• Doorways What dimensions/factors?
• Reach distances (controls) What percentile?

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Functional Anthropometry
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Functional Anthropometry
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Functional Anthropometry
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Interindividual Variation

• Resulting for DNA (Genotype/Phenotype)
• Environment
• Altitude, temperature, sunlight, soil type
• Nutrition
• Ethnicity

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Intraindividual Variation

• Aging
• Growing years increase in stature, weight, and
  other dimensions
• Early adulthood dimensions remain somewhat
  stable
• Later years decrease in height, increase in
  circumference and external diameters of bones
• Daily stature variation

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Changes In Stature
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Secular Variation

• During each decade of the 20th century, the US
  and Europe witnessed
• 1 cm increase in stature
• 2 kg increase in body mass
• Improvements in living conditions (hygienic and
  nutritional), changes in nutrition and activity
  levels
• Design-wise of little importance

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Changes In Stature
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Data Variations

• Inconsistency in
• Sampling, measurement, recording, sorting,
  analysis, reporting
• Effects to measures of central tendency (mean,
  median, mode)
• Can check to see if favorable coefficient of
  variation if data seems to be at odds

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Changing population

• Age, health, strength
• Increased females in the workplace
• Occupations (trends toward service sector in US)
• Baby boom
• Movement w/in the US

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Designing to fit the body

• Normal distribution often used to describe
  certain measures (depends on sample size)
• Central Limit Theorem
• There is no true average human
• Use the following steps
• Select measurements that relate to the design
• Determine if design is to fit a certain
  percentile or a range
• Combine values to ascertain compatibility
• Determine if one design will fit all users

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The Story of Lacy and Andrew

• Does one size fit all?
• Lacy is 4 10 (147 cm)
• Andrew is 6 10 (208 cm)

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Love conquers all even anthropometry!
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Available Body Size Data

• Dimensions for 1988 US Army personnel
• Table 1-10a (Tables 1-10 b and c for comparison)
• North American
• Main difference is weight
• Chest depth, Abdominal depth, Hip breadth
• 5th, 50th, 95th percentile measures (p) and
  standard deviation (s)
• Most populations not thoroughly measured (small
  n)
• Mean and standard deviation not true indicators
  of underlying population

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Using Percentiles

• Since most body dimensions are normally
  distributed, follows a symmetric bell curve

• May find skewed or binomial distributions if plot
  measurements, different techniques used

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Using Percentiles

• Because normality often assumed, can use mean (m)
  and standard deviation (s) to make develop
  measurements

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Using Percentiles

• Determine Single Point
• Select desired percentile
• Determine k (Table 1-8)
• Calculate P

• Determine Range
• Select upper and lower percentile
• Determine kmax and kmin
• Calculate Pmax and Pmin
• Range Pmax - Pmin

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Anthropometry Problem 1

• Instructor Combs is 510 tall. What percentile
  is his stature among US Adult males?

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Anthropometry Problem 2

• What is the stature of a 95 percentile female?

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Anthropometry Problem 3

• What range should be designed for an adjustable
  height work station for the 10th percentile
  female to the 90th percentile male?

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Statistical Body Models

• Assuming 5th percentile stature is directly
  related to all 5th percentile measures is
  incorrect
• Regression can lead to suitable models

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Motions and Postures

• Maintaining any posture for an extended time
  (static posture) is not good, we are designed to
  move.
• Spinal disc pressure lower when standing than
  sitting, but circulatory demands higher
• Laying down refreshes spinal discs and joints
• Mobility
• Effected by age, health, fitness, training,
  skill, previous injury

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Motions and Postures

• Design for movement
• Avoid twisted positions, esp. trunk and neck
• Avoid forward bending of trunk and neck
• Avoid static postures, esp. at extremes
• Avoid holding arms raised

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Questions?
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