AnthropometryAnthropometry

InitiativeInitiative ImaginationImagination NeedsNeeds DexterityDexterity IntelligenceIntelligence And so forthAnd so forth

Visual acuityVisual acuity DeterminationDetermination Upper back Upper back

strengthstrength AgeAge Leg lengthLeg length

AnthroposAnthropos (human) + (human) + metreinmetrein (to measure) (to measure)The study of how people vary inThe study of how people vary in

Engineering AnthropometryEngineering Anthropometry

Physical body size Physical body size – StaticStatic

Two dimensionalTwo dimensional Three dimensionalThree dimensional

– FunctionalFunctional

StrengthStrength – IsometricIsometric– Dynamic – isotonic, iso- Dynamic – isotonic, iso-

kinetic, iso-inertial etc.kinetic, iso-inertial etc.– MVC joint torquesMVC joint torques

Biomechanical / inertial properties Biomechanical / inertial properties – Segment massSegment mass– Segment center of gravity locationsSegment center of gravity locations– Muscle attachment sites and lever armsMuscle attachment sites and lever arms– Failure stresses of ligaments, tendons, bones Failure stresses of ligaments, tendons, bones

etc.etc.

Selection vs. Job Selection vs. Job ModificationModification Two basic strategies:Two basic strategies:

– Selection—fit the person to the job.Selection—fit the person to the job.– Job modification—fit the job to the Job modification—fit the job to the

personperson Follow the second strategy: the Follow the second strategy: the

key to progress has been to key to progress has been to challenge the environment.challenge the environment.

Exclude as Few as Exclude as Few as PossiblePossible Minimizes the number of people Minimizes the number of people

excluded, which tends to make excluded, which tends to make the job easier for everyonethe job easier for everyone

Balance seriousness of exclusion Balance seriousness of exclusion with cost of inclusionwith cost of inclusion

Excluded PercentileExcluded Percentile

May be: May be: – Upper (a door tall people can’t fit under)Upper (a door tall people can’t fit under)– Lower (a task requiring manual dexterity)Lower (a task requiring manual dexterity)– Both (intelligence test for factory job)Both (intelligence test for factory job)

Designing for the mean may exclude Designing for the mean may exclude half the population.half the population.

Population DimensionsPopulation Dimensions Define the user population.Define the user population. Consider the source of population Consider the source of population

dimensionsdimensions– Male/femaleMale/female– Military/civilianMilitary/civilian– AgeAge– EthnicityEthnicity– OccupationOccupation

Body Position Body Position DescriptionsDescriptions PlanesPlanes

– Saggital – divides the body into left and Saggital – divides the body into left and right half (medial/lateral)right half (medial/lateral)

– Coronal – divides the body into front and Coronal – divides the body into front and back half (anterior/posterior)back half (anterior/posterior)

– Transverse – divides the body into top and Transverse – divides the body into top and bottom half (superior/inferior)bottom half (superior/inferior)

LimbsLimbs– Proximal: close to torsoProximal: close to torso– Distal: further from torsoDistal: further from torso

Wrist/Hand MotionsWrist/Hand Motions

Flexion – closes the joint angle from neutral position.Flexion – closes the joint angle from neutral position. Extension – opens the joint angle from neutral position.Extension – opens the joint angle from neutral position. Adduction/ abduction – opens and closes laterallyAdduction/ abduction – opens and closes laterally

Wrist/Hand MotionsWrist/Hand Motions

Radial deviation/ulnar deviationRadial deviation/ulnar deviation

Wrist/Hand MotionsWrist/Hand Motions

Pronation/supinationPronation/supination

Body DimensionsBody Dimensions Sample 95th percentile dimensions (cm) of nude

U.S. adult civilians.

Female Male

Stature (height) 173.73 186.65

Eye height 162.13 174.29

Thigh height (sitting) 18.02 18.99

Forward reach 79.67 86.70

Hip breadth (sitting) 43.22 41.16

Weight (kg) 84.8 99.3

Variations in body Variations in body dimensionsdimensions

Most body dimensions do not correlate Most body dimensions do not correlate well with stature, coefficient of well with stature, coefficient of determination Rdetermination R22 is less than 50%. So be is less than 50%. So be careful when predicting other dimensions careful when predicting other dimensions from stature.from stature.

Individual segment weights are calculated Individual segment weights are calculated from total body weight.from total body weight.

In absence of data female may be In absence of data female may be estimated as 93% of male if no data estimated as 93% of male if no data availableavailable

Variations in StrengthVariations in Strength Females average 63% isometric strength of Females average 63% isometric strength of

males.males. Strength of specific muscle groups varies Strength of specific muscle groups varies

depending ondepending on– Limb: Leg approx. 3 times strength of armLimb: Leg approx. 3 times strength of arm– Direction exerted: Strength may decrease by Direction exerted: Strength may decrease by

50% 50% – Preferred hand/arm/leg: Strength may vary by Preferred hand/arm/leg: Strength may vary by

40–50%40–50% Left and right leg strengths do not differ Left and right leg strengths do not differ

appreciably.appreciably.

Other CharacteristicsOther Characteristics

AgeAge Personal spacePersonal space

Age of WorkforceAge of Workforce

Birth rate is declining.Birth rate is declining. Additional workers must come Additional workers must come

from immigrationfrom immigration Longer work hoursLonger work hours Delayed retirementDelayed retirement Older workers must be Older workers must be

considered.considered.

Personal SpacePersonal Space Intimate (0 – 18 in.)Intimate (0 – 18 in.) Personal (18 – 48 in.)Personal (18 – 48 in.) Social (4 – 12 ft)Social (4 – 12 ft) Public (> 12 ft)Public (> 12 ft) Boundaries vary with gender, Boundaries vary with gender,

familiarity, and culture.familiarity, and culture.

Statistical CalculationsStatistical Calculations Normal distribution provides a Normal distribution provides a

close approximation.close approximation. Mean (average) is 50th percentile.Mean (average) is 50th percentile. Normal distribution is symmetrical.Normal distribution is symmetrical. Absolute variability given by Absolute variability given by

standard deviation.standard deviation. Relative variability given by Relative variability given by

coefficient of variation.coefficient of variation.

Normal DistributionNormal Distribution

Distribution Distribution CalculationsCalculations To Find PercentileTo Find Percentile

– Find difference from the mean Find difference from the mean (subtract).(subtract).

– Convert to standard units (divide by Convert to standard units (divide by standard deviation).standard deviation).

– Use table to find percentile.Use table to find percentile.

Distribution Distribution CalculationsCalculations To Find DimensionTo Find Dimension

– Use table to find number of standard Use table to find number of standard units from mean.units from mean.

– Convert to dimension measure Convert to dimension measure (multiply by standard deviation).(multiply by standard deviation).

– Add or subtract mean.Add or subtract mean.