section 14 contents 14 anthropometry and · pdf filehfdg section 14 contents january 15, 1996...

HFDG Section 14 contents

January 15, 1996 FAA William J. Hughes Technical Center 14-i

Section 14 contents

14 Anthropometry and biomechanics ............................. 14-1

14.1 Generalapplication ofanthropometricandbiomechanicaldata ............................................................................................... 14-1

14.1.1 Userpopulation ............................................................................................... 14-1

P 14.1.1.1 Use of data ............................................................... 14-2P 14.1.1.2 Data to be used ........................................................ 14-2P 14.1.1.3 Using population extremes ...................................... 14-2

14.1.2 Usingdesign limits ............................................................................................... 14-2

P 14.1.2.1 Selecting the correct human physical and associated measurement characteristics .................... 14-3

P 14.1.2.2 Selecting the appropriate distribution information ............................................................... 14-4

P 14.1.2.3 Selecting the correct percentile statistic ................... 14-4P 14.1.2.4 Clearance dimension at the 95th percentile .............. 14-6P 14.1.2.5 Clearance dimension at the 99th percentile .............. 14-7P 14.1.2.6 Limiting dimension at the 5th percentile ................. 14-7P 14.1.2.7 Limiting dimension at the 1st percentile .................. 14-7P 14.1.2.8 Adjustable dimensions ............................................. 14-7P 14.1.2.9 Sizing determinations .............................................. 14-7P 14.1.2.10 Critical life support equipment ................................ 14-8

14.1.3 Avoidingpitfalls in applyinganthropometric data ............................................................................................... 14-8

P 14.1.3.1 Misuse of the 50th percentile or of the average ....... 14-8P 14.1.3.2 Misperception of the typically sized person ............. 14-8P 14.1.3.3 Summation of segment dimensions ......................... 14-8

Section 14 contents HFDG

14-ii FAA William J. Hughes Technical Center January 15, 1996

14.1.4 Solving acomplex sequence ofdesign problems ............................................................................................... 14-9

P 14.1.4.1 Design to body positions and motions of the tasks .......................................................................... 14-9

P 14.1.4.2 Construction or collection of unique position data ........................................................................... 14-9

P 14.1.4.3 Design reference points and zones ........................... 14-9R 14.1.4.4 Building and using reach envelopes ....................... 14-10R 14.1.4.5 Building visual envelopes or footprints ................. 14-10R 14.1.4.6 Building design solutions ...................................... 14-10P 14.1.4.7 Effects of clothing ................................................. 14-10

Exhibit 14.1.4.7 Additive effects of clothing on anthropometric measures ............................................. 14-11

P 14.1.4.8 Effects of tools and equipment lifted or carried ..... 14-12

14.1.5 Use ofdistribution andcorrelation data ............................................................................................. 14-13

R 14.1.5.1 Gaussian distribution of measurement values on a single human physical characteristic .................... 14-13

Exhibit 14.1.5.1 Percentile values .................................... 14-13

R 14.1.5.2 Using bivariate distribution data ............................ 14-13R 14.1.5.3 Use of correlation and multiple

correlation data ....................................................... 14-14

14.1.6 Use of models ............................................................................................. 14-14

P 14.1.6.1 Data applicable to the design problem ................... 14-15P 14.1.6.2 Common errors ...................................................... 14-15P 14.1.6.3 Use of design limits approach ................................ 14-15P 14.1.6.4 Model treatment of multiple variables ................... 14-15P 14.1.6.5 Joint mobility and reach interaction ....................... 14-15

14.2Anthropometricvariability factors ............................................................................................. 14-15

R 14.2.1 Foreign populations .................................................. 14-15R 14.2.2 Race ......................................................................... 14-15R 14.2.3 Body slump .............................................................. 14-15


January 15, 1996 FAA William J. Hughes Technical Center 14-iii

14.3Anthropometricandbiomechanicaldata ............................................................................................. 14-16

14.3.1 Data usage ............................................................................................. 14-16

P 14.3.1.1 Use of anthropometric and biomechanical data ..... 14-16P 14.3.1.2 Task considerations ............................................... 14-16

14.3.2 Static bodycharacteristics ............................................................................................. 14-16

R 14.3.2.1 Static data .............................................................. 14-16

Exhibit 14.3.2.1 Static human physical characteristics (head) ........................................................ 14-18

Exhibit 14.3.2.1 Static human physical characteristics (seated) ...................................................... 14-22

Exhibit 14.3.2.1 Static human physical characteristics (standing) .................................................. 14-26

Exhibit 14.3.2.1 Static human physical characteristics (standing position and hands) .................... 14-30

P 14.3.2.2 Relevant static anthropometric data ....................... 14-17

14.3.3 Dynamic(mobile) bodycharacteristics ............................................................................................. 14-30

14.3.3.1 Rangeof whole body motion ............................................................................................. 14-30

P 14.3.3.1.1 Trunk movement ................................................. 14-31P 14.3.3.1.2 Whole body movement ....................................... 14-31

14.3.3.2 Joint motion ............................................................................................. 14-31

P 14.3.3.2.1 Single joint movements ....................................... 14-31

Exhibit 14.3.3.2.1 Joint movement ranges ........................ 14-32

P 14.3.3.2.2 Range of motion for two joints ............................ 14-34

Exhibit 14.3.3.2.2 Change in range of joint movement with movement in an adjacent joint ................ 14-35

P 14.3.3.2.3 Design limit approach ......................................... 14-35

Section 14 contents HFDG

14-iv FAA William J. Hughes Technical Center January 15, 1996

P 14.3.3.2.4 Use of this guide’s dynamic data ......................... 14-36

14.4 Reach ............................................................................................. 14-36

P 14.4.1 Task and body position effects ................................. 14-36R 14.4.2 Reach envelope data collection ................................ 14-37

Exhibit 14.4.2 Reach envelopes in vertical and horizontal planes .............................................................. 14-37

P 14.4.3 Reach envelopes for control actions ......................... 14-38P 14.4.4 Reach envelope interaction with the reach task ........ 14-38

Exhibit 14.4.4 (a) Touch, grip, and grasp functions that interact with arm reach ............................... 14-38

Exhibit 14.4.4 (b) Thumb and forefinger grasp boundary data for females in the 46 cm and 61 cm horizontal planes .................................. 14-40

Exhibit 14.4.4 (c) Thumb and forefinger grasp boundary data for females in the 0 and -15 cm vertical planes ............................................. 14-41

R 14.4.5 Strength or fine manipulation ................................... 14-42

14.5 Humanstrength andhandling capacity ............................................................................................. 14-42

14.5.1 Musclestrength factors ............................................................................................. 14-42

14.5.2 Exertedforces ............................................................................................. 14-43

R 14.5.2.1 Maximum young male force or resistance for a control ............................................................ 14-43

Exhibit 14.5.2.1 Male muscle strength of the arm, hand, and thumb for control forces (5th percentile values) ...................................................... 14-44

P 14.5.2.2 Increasing strength values ...................................... 14-45P 14.5.2.3 Decremented strength values ................................. 14-46R 14.5.2.4 Comparative strength ............................................. 14-46R 14.5.2.5 Preventing tremor in positive control

performances .......................................................... 14-46

14.5.3 Push andpull forces ............................................................................................. 14-47

R 14.5.3.1 Horizontal direction of force .................................. 14-45


January 15, 1996 FAA William J. Hughes Technical Center 14-v

Exhibit 14.5.3.1 Horizontal push and pull forces that can be exerted ............................................................ 14-47

R 14.5.3.2 Vertical direction of force ...................................... 14-48

Exhibit 14.5.3.2 Static muscle strength data for vertical pull exertions .................................................. 14-49

R 14.5.3.3 Forces for handles .................................................. 14-48

14.5.4 Lifting andcarrying ............................................................................................. 14-52

P 14.5.4.1 Lifting and carrying limits ..................................... 14-52

14.6 Design forphysical comfort ............................................................................................. 14-52

R 14.6.1 Adjustment capabilities ............................................ 14-52R 14.6.2 Restrictions to movement ......................................... 14-52R 14.6.3 Body support ............................................................ 14-53P 14.6.4 Body posture ............................................................ 14-53P 14.6.5 Demands upon tasks ................................................. 14-53

HFDG 14 Anthropometry and biomechanics

January 15, 1996 FAA William J. Hughes Technical Center 14-1

14 Anthropometry and biomechanicsDesigners and human factors specialists incorporate scientificdata on human physical capabilities into the design of systemsand equipment. Human physical characteristics, unlike those ofmachines, cannot be designed. However, design oversight canplace unnecessary demands and restrictions upon user personnel.

Definitions. Anthropometry is the scientificmeasurement and collection of data about human physicalcharacteristics and the application (engineeringanthropometry) of these data in the design and evaluationof systems, equipment, manufactured products, human-made environments, and facilities. Biomechanicsdescribes the mechanical characteristics of biologicalsystems, in this case the human body, in terms of physicalmeasures and mechanical models. This field isinterdisciplinary (mainly anthropometry, mechanics,physiology, and engineering). Its applications addressmechanical structure, strength, and mobility of humans forengineering purposes.

This final technical section of the HFDG provides additionalanthropometric and biomechanics data beyond that used inprevious technical sections. Previous data are cross referenced,where appropriate. Unlike the other sections, this sectionprovides more guidance about the nature of the data, its selection,and its proper use. It provides rules for applying the vast amountof human form data available to specific design fit, function, andhuman task performance.

The section also covers application principles and their resultingrules, human body measurement data (static and dynamic), rangeof motion and strength data, as well as comfort information.

14.1 Generalapplication ofanthropometricandbiomechanicsdata

In this document, body size, strength, and mobility data arepresented to represent the current FAA maintenance population.In the future, this population will include a wider range of ethnicbackgrounds. Minorities and females are expected to increase.The average age is expected to decrease. These changes will beimportant for future systems design.

In this general section, design criteria and guidelines are givenfor: (1) ascertaining user population data, (2) using the designlimits approach, (3) avoiding pitfalls in applying the data, (4)using distribution and correlation data, (6) solving designproblems, and (7) using models.

14.1.1 Userpopulation

Anthropometric data are most appropriate when they are derivedfrom a survey of the existing worker population of interest. Sincethe sub-population associated with the FAA has not beensurveyed, information from substitute sources is used as a basisfor design.

14 Anthropometry and biomechanics HFDG

14-2 FAA William J. Hughes Technical Center January 15, 1996

P 14.1.1.1 Use of data. Anthropometric and biomechanics datashall be used in the design of systems, equipment (includingpersonal protection equipment), clothing, workplaces,passageways, controls, access openings, and tools.

Discussion. The human’s interface with other systemcomponents needs to be treated as objectively andsystematically as are other interface and hardwarecomponent designs. It is not acceptable to guess abouthuman physical characteristics or to use the designer’sown measurements or the measurements of associates.Application of appropriate anthropometric andbiomechanics data is expected.

P 14.1.1.2 Data to be used. Designers and human factorsspecialists shall use the anthropometric and biomechanics dataprovided in this guide. If additional data are needed, they shalluse the more complete data given in DoD-HDBK-743. If otherreference or new data collections are considered, the contractorshall obtain the approval of the acquisition program office.

Discussion. If this guide does not present data needed forthe problem at hand, the designer will have to selectappropriate sample information from DoD-HDBK-743.In that handbook, the 1988 military male and femalesurvey distributions can be used to represent FAAmaintenance personnel when needed, as it represents themost comprehensive samples available. Note that civilianworking populations could be expected to have a largerrange of sizes and ages than the military. Samples withcomprehensive measures are not available.

P 14.1.1.3 Using population extremes. Designers and humanfactors specialists shall draw upon the extremes of the larger malepopulation distribution and the extremes of the smaller femalepopulation distributions to represent the upper and lower rangevalues, respectively, to apply to anthropometric andbiomechanics design problems.

Discussion. The use of separate male and femalepopulation data is a conservative approach that results inmore inclusive design dimensions than the samepercentiles would from a composite population.

14.1.2 Usingdesign limits

Initial rules in this section address the design limits approach. Tounderstand this approach it is helpful to consider the overall stepsand choices that one makes in applying anthropometric andbiomechanics data. The design limits approach entails selectingthe most appropriate percentile values in population distributionsand applying the appropriate associated data in a design solution.These steps are listed in this introductory material and areexplained in detail in the initial three guidelines of thissubsection. If the reader has applied the design limit approachand understands it, the reader can skip the rest of thisintroductory material as well as the explanations associated withthe first three guidelines, do not skip the guidelines.



Definition. The design limits approach is a method ofapplying population or sample statistics and data abouthuman physical characteristics to a design so that adesired portion of the user population is accommodatedby the design. The range of users accommodated is afunction of limits used in setting the population portion.

To understand the design limits approach it is helpful to considerstep by step the choices that design personnel make in applyingthese human physical data.

a. Select the correct human physical characteristic and itsapplicable measurement characteristic (description) forthe design problem at hand.

b. Select the appropriate population, representativesample, or guideline information on the selected humanphysical characteristic and measurement description toapply to the design problem.

c. Determine the appropriate statistical point(s), usuallypercentile points from guideline information or from thesample distribution(s) in order to accommodate a desiredrange of the human characteristic within the distributionof the user population.

d. Read directly or determine statistically the measurementvalue(s) that corresponds to the selected statisticalpoint(s) relevant to the population distribution.

e. Incorporate the measurement value as a criterion for thedesign dimension, or in the case of biomechanics data,for the movement or force solution in the design problem.

The design limits approach is accomplished during the selectionof percentile value(s) as the statistical point(s) in step c above.Steps (a) and (b) are explained under the first two rule paragraphsbelow. Steps (c), (d) and (e) are explained under the third ruleparagraph below. The terms in bold above are defined in therules that follow. An example problem covering all steps followsthe third rule in paragraph 14.1.2.3. Different percentile valuesapply to design issues involving clearance, reach limits,adjustments, and sizing. These types of design limits problemsare covered in paragraphs 14.1.2.4 through 14.1.2.9.

P 14.1.2.1 Selecting the correct human physical and associatedmeasurement characteristics. Design personnel shall selecthuman and measurement characteristics that are relevant to thecomponent of design under consideration and are based upon:

a. an analysis of human tasks associated with the system,equipment, facility, or environment,

b. consideration of normal, degraded, or emergency modesof task activities, and



c. consideration of the importance and frequency ofexpected task performance.

Definitions. Human physical and associatedmeasurement characteristics refer to specific physical,mobility, or strength features of human users and to theexplicit way that a human feature or capability ismeasured for use as general anthropometric orbiomechanics data or as data for a specific design.

Explanation. (Step a from 14.1.2). Select the correcthuman physical characteristic and its applicablemeasurement description for the design problem at hand.The associated measurement description tells howmeasurements are taken for population or sampledistribution data. The decision to use a particularcharacteristic is one of selecting the correct variable(s) forthe problem. If the problem calls for biomechanicsinformation, for example, strength information, the sameinitial step of identifying the specific human characteristicand how it is measured would apply.

P 14.1.2.2 Selecting the appropriate distribution information.When the design limits approach is used, designers and humanfactors specialists shall select the appropriate sample distribution(including the male, female, and nationality compositions) fromguideline, handbook, or survey sources.

Discussion. Information presented in this guide isderived from the most relevant distributions for the usersand for the general problem areas. Part of the selectionprocess may be to choose the most appropriate male orfemale distribution information.

Explanation. (Step b from 14.1.2). Select theappropriate population, representative sample, orguideline information appropriate for guideline data onthe selected human physical characteristic and itsmeasurement description that applies to a design problem.

A population distribution has certain definingparameters. For instance, a population mean and varianceare sufficient to define a known normal (or Gaussian)distribution (the bell shaped curve associated with thevariability of many human characteristics).

Usually, the entire population of users has not beenmeasured so sample distribution data and statistics aregenerally used. Information from large samples canestimate population parameters and thus can be used.

P 14.1.2.3 Selecting the correct percentile statistic. Designcriteria for a human physical integration problem shall be basedupon the range of the population to be accommodated. Designersand human factors specialists shall determine the appropriatestatistical points, usually percentile statistics, to accommodate an



appropriate range of the population distribution for the specificdesign problem.

Definitions. The percentile statistic is determined byranking all data values (using the applicable measurementvalues related to the selected human physicalcharacteristic) in the sample and determining thepercentage of data that fall at or below a specific datumvalue. This percentage is known as the percentile value(or point) of the selected datum.

By definition, the point below which five percent of thedata values fall is known as the 5th percentile statistic.The point below which one percent of the data falls isknown as the 1st percentile. Similarly, the midpoint ofthe distribution is the point below which 50 percent of thedata falls and is defined as the 50th percentile. Toaccommodate 95 percent of the population or sample,choose the 95th percentile statistic, to accommodate allbut the top one percent choose the 99th percentilestatistic.

Explanation. (Step c from 14.1.2). Determine theappropriate statistical point(s), usually percentile points,from guideline information or from a sample distribution,in order to accommodate the desired range of the humancharacteristic within the distribution of the userpopulation.

Usually, for design purposes, it is impractical toaccommodate the extremes of the distribution becausethere is so much variability at the extremes and so fewcases. often, persons who are extreme in dimensionalmeasurement values (in the lowest or highest one percent)know it, and they behave so as to compensate for thedesigned portions of their environments.

In step c, designers select the most applicable statisticalpoint(s) from the appropriate distribution to accommodatethe portion of the population that is appropriate to thedesign problem. The design limits approach involvesselecting the appropriate percentile statistic(s). It waspreviously noted that different kinds of design problems(clearance, reach, adjustment, and sizing) call for differentstrategies and result in the selection of different percentilestatistics.

(Step d). Read directly or determine statistically theappropriate measurement value (or datum value) thatcorresponds to the selected statistical point relevant to thepopulation (or applicable sample) distribution.

For any percentile statistic used as applicable to a designproblem, there is a measurement value or data point thatcorresponds to the criterion percentile statistical value.This measurement value can be calculated or counted



from the rank order data distribution, or it can be readdirectly from a tabular or graphical representation of thedistribution.

If population distribution characteristics (for example,normality) and population parameters (for example, meanand variance) are known, then other statistical propertiescan be determined (for instance, percentiles andassociated measurement values (see paragraph 14.1.5.1).

(Step e). Incorporate the measurement value as acriterion for the design dimension (or, in the case ofbiomechanics data, for the movement or force solution) inthe design problem.

The actual measurement value is used as the designdimension, force, or movement solution to the designproblem at hand. Since the example design problem isone of accommodating the reach capabilities, the designerwill chose the female distribution to represent the shorterreach capabilities in the population.

Example. A designer who has an application probleminvolving human reach capabilities decides (step a) thatthe human physical characteristic "functional (thumb-tip)reach" is applicable to this reach problem. In this case theassociated measurement description is as follows: thehorizontal distance from the wall to the tip of the thumb ismeasured with the subjects’ shoulders against a wall, thearm extended forward, and the index finger touching thetip of the thumb. (See exhibit 14.3.2.1, physicalcharacteristic 43.) ( Step b) The designer would like tohave distribution information from a compositepopulation which includes both male and female data andwhich represents the applicable FAA population. Sinceno such survey data exist for this population, this guidedirects (14.1.1.2) that substitute distribution data forseparate male and female populations be used (see exhibit14.3.2.1). Since the example design problem is one ofaccommodating the reach capabilities, the designer in stepb will chose the female distribution to represent theshorter reach capabilities in the population. In step c themost appropriate percentile statistic would be the 5thpercentile of the female sample distribution. This pointwould assure that the reach of almost all male and femalepersonnel except those smaller than the 5th percentilefemale would be accommodated. In step d of theexample, the measurement value for the 5th percentilefemale is 67.7 cm (26.7 in) as read from exhibit 14.3.2.1,physical characteristic 43. In step e of the design exampleabove, the 67.7 cm (26.7 in) value would be used as thecriterion dimension in the design to accommodatepersonnel reach.

P 14.1.2.4 Clearance dimension at the 95th percentile. Designclearance dimensions which must accommodate or allow passage



of the body or parts of the body shall be based upon the 95thpercentile of the male distribution data.

P 14.1.2.5 Clearance dimension at the 99th percentile. If acertain clearance design dimension is critical to the activities ofthe entire population or could be life threatening to likely userswho are at the larger extremes of the distribution, then a humanmeasurement value that is at least the 99th percentile male shallbe used as the criterion design dimension.

Discussion. Whole body clearance dimensions forfrequently used passageways and dimensions for criticalescape hatches need to be based on the 99th percentilestatistic. This practice ensures 99 percent of the userpopulation who are smaller than this measurement valuewill have proper clearance.

P 14.1.2.6 Limiting dimension at the 5th percentile. Limitingdesign dimensions, such as reach distances, control movements,display and control locations, test point locations, and handrailpositions, that restrict or are limited by body or body part size,shall be based upon the 5th percentile of female data forapplicable body dimensions.

Discussion. For example, the maximum height from floorlevel to an accessible part of any piece of equipment needsto be within reach of the 5th percentile female maintainer,which will ensure that at least 95 percent of the userpopulation can access this part of the equipment.

P 14.1.2.7 Limiting dimension at the 1st percentile. If certainlimiting design dimensions are critical to the activities of theentire population or could be life threatening to likely users whoare at the smaller extremes of the applicable distribution, then the1st percentile of the female distribution shall be used as the basisfor the criterion dimension.

Discussion. Dimensions for reaching emergency orlifesaving equipment are examples where access cannotbe denied to the smaller extremes of the population.

P 14.1.2.8 Adjustable dimensions. Any equipment dimensionsthat need to be adjusted for the comfort or performance of theindividual user shall be adjustable over the range of the 5th to95th percentiles.

P 14.1.2.9 Sizing determinations. Clothing and certain personalequipment dimensions that need to conform closely to thecontour of the body or body parts shall be designed and sized toaccommodate at least the 5th through the 95th percentile range.If necessary, this range shall be accommodated by creating anumber of unique sizes, where each size accommodates asegment of the population distribution. Each segment can bebounded by a small range of percentile values.



P 14.1.2.10 Critical life support equipment. Dimensions or sizesof critical life support equipment shall accommodate, at least, therange defined by the 1st through the 99th percentiles of thedistribution.

14.1.3 Avoidingpitfalls in applyinganthropometric data

There are several common errors to be avoided by designerswhen they apply anthropometric data to design. These are: (1)designing to the midpoint (50th percentile) or average, (2) themisperception of the typical sized person, (3) generalizing acrosshuman characteristics, and (4) summing of measurement valuesfor like percentile points across adjacent body parts.

P 14.1.3.1 Misuse of the 50th percentile or of the average. The50th percentile or mean shall not be used as design criteria as itaccommodates only half of the users.

Discussion. When the population distribution is Gaussian(normal), the use of either the 50th percentile or theaverage for a clearance would, at best, accommodate halfthe population.

P 14.1.3.2 Misperception of the typically sized person. Designersor human factors specialists shall not use the concept of atypically sized person where the same percentiles values areexpected across many dimensions. A person at the 95 percentilein height is unlikely to measure at the 95th percentile in reach orother dimensions. A percentile value and its measurement valuethat pertains to a particular body part shall be used exclusivelyfor functions that relate to that body part.

Discussion. When the middle 30 percent of a populationof 4000 men was measured on 10 dimensions, only one-fourth of them were "average" in a single dimension(height), and less than 1 percent were average in fivedimensions (height, chest circumference, arm length,crotch height, and torso circumference). Keeping in mindthat there is not an "average person," one also must realizethat there is not a "5th percentile person" nor a "95thpercentile" person. Different body part dimensions arenot necessarily highly correlated. An implication is thatone can not choose a person who is 95 percentile instature as a test subject for meeting 95 percentilerequirements in reach or other dimensions.

P 14.1.3.3 Summation of segment dimensions. Summation of likepercentile values for body components shall not be used torepresent any human physical characteristic that appears to be acomposite of component characteristics.

Discussion. The 95th percentile arm length, for instance,is not the addition of the 95th percentile shoulder-to-elbow length plus the 95th percentile elbow-to-handlength. The actual 95th percentile arm length will besomewhat less than the erroneous summation. Todetermine the 95th percentile arm length, one must use a



distribution of arm length rather than component partdistributions.

14.1.4 Solving acomplex sequence ofdesign problems

In this section, rules are presented for approaching complexdesign problems that requires the consideration of a sequence ofrelevant design reference locations (such as seat reference pointsand eye reference zones), human physical characteristics,statistical points, and measures. The recommended approachinvolves identifying the necessary human activities and positionsand establishing reference points and envelopes for the necessaryactivities. These envelopes impact the location and design ofcontrols and displays as well as the placement of work surfaces,equipment, and seating accommodations. The effects of clothingor carried equipment are then used to expand the dimensions.

P 14.1.4.1 Design to body positions and motions of the tasks.Design personnel shall base the necessary operator andmaintainer body positions and motions on personnel tasks to beperformed during normal, degraded, and emergency modes ofoperations and maintenance. If the human physicalcharacteristics associated with common or mobile workingpositions as presented and illustrated in section 9.4 are applicableto the jobs and tasks, the associated distribution and measurementvalues shall be used.

P 14.1.4.2 Construction or collection of unique position data. Ifthe common and mobile working positions data in section 9.4 ofthis guide do not represent the unique working positionsassociated with a design, then design personnel shall constructthe applicable human physical characteristics and measures fromthe static and dynamic data provided later in sections 14.3.2 and14.3.3 or in DoD-HDBK-743. If no applicable data can be foundor calculated for important design measures, then, with the priorapproval of the acquisition program office, sample measures shallbe taken on appropriate personnel for the unique workingpositions.

Discussion. Anthropometric measurement needs to bedone by professionals because there are manycomplexities and potential interactions among positions ofbody segments, as well as many technical points andpitfalls to avoid in measurement practice. Samplemeasurement methods can be found in Roebuck,Kroemer, and Thomas, 1975.

P 14.1.4.3 Design reference points and zones. Design referencepoints or zones that are key to the relationship betweenpersonnel and hardware or facility design shall be based upon theanthropometry of the necessary working positions. Suchreference points and zones include seat reference points, armrotation points, eye reference points or zones, visual envelopes,and mobility or comfort adjustment ranges. These referencepoints may have design practice definitions in certain applicationarea such as cockpit design or commercial seating. Thesestandard practices can be used, when applicable. However forboth standard or unique designs practices, explicit definitions



used shall accompany each specific application project and therelationships between these points or zones, user physicalcharacteristics, and task requirements shall be explicit.

R 14.1.4.4 Building and using reach envelopes. If reach dataprovided in this guide (see section 14.4) do not apply to a specificdesign problem, then reach design dimensions or envelopes fordesign use should be constructed considering:

a. one-handed or two-handed operation,

b. grasp requirements which may affect the functional reachenvelope,

c. positional relationship of a shoulder reference point orarm rotation point to the seat back, seat reference point, orother posture reference or design reference points, and

d. the appropriate samples and anthropometricmeasurements from the data provided in this guide or inDoD-HDBK-743 (see paragraph 14.1.1.2).

R 14.1.4.5 Building visual envelopes or footprints. Once eyereference points and or zones are established, design personnelshould project the visual areas around the line of sight for visualtasks. Visual envelopes or footprints can show if equipmentlocations may interfere with necessary visual tasks. Similarly,they show where displays can be located to ensure appropriatelegibility and information use. Paragraph and exhibit 7.1.2.6.9address display locations in relation to line-of-sight perspectives.

R 14.1.4.6 Building design solutions. Many problems associatedwith integrating human physical characteristics into a designinvolve building a series of dimension criteria. If feasible, eachcriterion dimension should be based upon the design limitapproach to the appropriate single human physical characteristicfor the body segment appropriate to the design problem. Staticand dynamic data (see section 14.3) are used as the design detailsare planned and iterated. If appropriate, composite characteristicsand measures should be used as addressed in paragraph 14.1.5.3.

Discussion. In design work, measurements are seldomused alone. Sitting height and functional reach are used inthe design of consoles, while hip breadth, sitting andpopliteal height are required for the design of seating.

P 14.1.4.7 Effects of clothing. Because most anthropometric datapresented in this guide and in other data sources represent nudebody measurements (unless otherwise indicated), suitableallowances shall be made for light, medium, or heavy clothingand for any special protective equipment that is worn. Exhibit14.1.4.7 illustrates the additive effects of clothing on static bodydimensions and shows the 95th percentile gloved hand measures.If special items of protective clothing or equipment are involved,the effects shall be measured in positions required by the users’



tasks. The effects on the extremes of the population distributionshall be determined.

Discussion. Nude dimension and light clothing can beregarded as synonymous for practical purposes.Additional information on the changes in anthropometricmeasurement values imposed by different clothingensembles are found in Johnson, 1984.



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P 14.1.4.8 Effects of tools and equipment lifted or carried. Iftools or equipment are to be lifted or carried, the additive effectsof their dimensions upon the relevant human characteristics andmeasures shall be determined by taking into account:

a. how the tool or equipment may be lifted and carried,

b. the number of people involved in the carry or in the lift,

c. the tasks involving the tools or equipment, and

d. the effects on work passageways, areas, and stations.

14.1.5 Use ofdistribution andcorrelation data

Complex uses of statistical data concerning human physicaldimensions or capabilities are introduced in this section. Data anddistribution information on a single physical characteristic and itsmeasures provides no information about that characteristic’scomposite relationship with any other characteristic and itsmeasures. For design, the relationship between two or morecharacteristics and how their measures vary together is important.Consider sizing clothing and designing seats. Bivariatedistributions and correlation statistics can be used byknowledgeable professionals to determine design criteria.

R 14.1.5.1 Gaussian distribution of measurement values on asingle human physical characteristic. The relationship betweenthe Gaussian distribution and the measurement value equivalentto the desired percentile statistic value should best be determinedfrom a smoothed frequency distribution or from the formulapresented in exhibit 14.1.5.1 if the following conditions are met:

a. the percentile value is not given in applicable Human-machine-interface data, and

b. the population distribution for the applicable humanphysical characteristic is known to be Gaussian (normal)and the mean and variance are known.



R 14.1.5.2 Using bivariate distribution data. Bivariate datashould be professionally applied and interpreted since knowledgeof the population distribution characteristics are necessary toproject and extract design limits and to apply them to designproblems.

Discussion. The variability of two body measurementsand their interrelationship with each other may bepresented in a graph or a table. Bivariate informationincludes the ranges of two measurements and thepercentages or frequencies of individuals who arecharacterized by the various possible combinations ofvalues of the two measurements. Knowledgeableprofessionals can tell about the relationships from theappearance and shape of the joint distribution ofmeasures. Correlation statistics, when the relationshipwarrants, provides additional insight and when anappropriate samples are large enough may providepredictions of population values.

R 14.1.5.3 Use of correlation and multiple correlation data. Iftwo or more human physical characteristics are applicable to adesign problem, professionals should apply and interpretcorrelation statistics. Knowledge about distributions andintercorrelations among the distributions need to be factored intothe use of these data.

Discussion. The relationships or correlations betweenspecific body measurements are highly variable among thevarious human characteristics and may differ acrosssamples and populations. For example, breadthmeasurements tend to be more highly correlated withweight than with stature. The degree of the relationshipmay be expressed by a correlation coefficient or "r" value.

Although common percentile values may not be used tosum data across adjacent body parts, (see paragraph14.1.3.3), regression equations derived from theapplicable samples can be used in constructing compositebody measures.

Definition. The correlation coefficient or "r" valuedescribes the degree to which two variables vary together(positive correlation) or vary inversely (negativecorrelation). The correlation coefficient, "r", has a rangeof values from +1.0 (perfect positive correlation) through-1.0 (perfect negative correlation). Multiple correlationinvolves the predictable relationship of two or morevariables with another criterion variable (such as acomposite measurement value). "R" is the multiplecorrelation coefficient. It is recommended that onlycorrelations with strong predictive values be used (that iswhere r or R is at least or greater than |.7|). (Note: R2 is



the square of the multiple correlation coefficient andequates to the proportion of the variation accounted for inthe prediction. An R of .7 would account for about 50percent of the variation).

14.1.6 Use of models Models that represent human physical characteristics are beingused with increasing frequency in the design of equipment andsystems. Some models are as simple as drawing board manikinswith articulated joint movement. Others use computer graphics tomodel dynamic human physical characteristics in threedimensional workplaces. Other models are being developed tointegrate human physical characteristics into computer-aideddesign software.

P 14.1.6.1 Data applicable to the design problem. Designers andhuman factors specialists shall ensure that models of humanphysical characteristics contain and appropriately use accuratepopulation, sample, or guideline-based data for the userpopulation and the design problem of interest.

P 14.1.6.2 Common errors. Designers and human factorsspecialists shall ensure that neither the model to be used nor themanner of its use violates the design criteria about commonanthropometric pitfalls stated in section 14.1.3.

P 14.1.6.3 Use of design limits approach. Designers and humanfactors specialists shall ensure that models employed in designappropriately use the design limits method.

P 14.1.6.4 Model treatment of multiple variables. If multivariatetreatments are appropriate to a design problem, designers andhuman factors specialists shall ensure that the modelsappropriately treat and use the proper multivariate data.

P 14.1.6.5 Joint mobility and reach interaction. Designers andhuman factors specialists shall ensure that the modelsappropriately treat joint mobility and reach (see subsections14.3.3.2 and 14.4).

14.2Anthropometricvariabilityfactors

There are many factors that relate to the large variability observedin measures of the human body. These factors include: (1) bodyposition, (2) age, health, and body condition, (3) sex, (4) race andnational origin, (5) occupation, and (6) evolutionary trends.These factors affect future population sampling and encouragethe use of the most recent data on the populations of interest. Ifdesigners and human factors specialists need to draw upon otherdata or accomplish some special purpose sampling, the followingguidelines related to data variability may assist.

R 14.2.1 Foreign populations. If a specific use of the system orequipment involves operation or maintenance by foreignpersonnel in locations outside the United States, sample datashould be obtained that represents the foreign work force.

R 14.2.2 Race. There are no practical differences between theanthropometric characteristics of the U.S. Afro-American



population and the U.S. population as a whole. Thus no specialdata collections or data adjustment should be used toaccommodate the integrated U.S. work population.

R 14.2.3 Body slump. In determining body position and eyeposition zones for seated or standing positions, a slump factorwhich accompanies relaxation should be taken into account.Seated-eye height measurements can be reduced by as much as 65mm (2.56 in) when a person sits in a relaxed position. Bodyslump, when standing, reduces stature as much as 19 mm (.75 in)from a perfectly erect position. These slump factors should beconsidered in designing adjustable seats, visual envelopes, anddisplay locations.

14.3Anthropometricandbiomechanicsdata

This section provides general guidance for the use of specificanthropometric and biomechanics data, static body characteristicsdata, dynamic body characteristic data including range of jointmotion and common and mobile working positions.

Dimensions of the human body which influence the design ofpersonal and operational equipment are of two types: (1) staticdimensions, which are measurements of the head, torso, andlimbs in normal positions, and (2) dynamic dimensions, whichare measurements taken in working positions or duringmovement.

14.3.1 Data usage

P 14.3.1.1 Use of anthropometric and biomechanics data. Datathroughout section 14.3 are to be used for anthropometric issuesthat are not addressed in earlier sections of this HFDG. Ifdesigners and human factors specialists need additional data tosolve anthropometric design problems associated with humanphysical characteristics they shall use the data presented in DoD-HDBK-743 (see also 14.1.1.2).

P 14.3.1.2 Task considerations. Designers and human factorsspecialists shall take the following task conditions intoconsideration when using the human physical characteristic datapresented in this section:

a. the nature, frequency, and difficulty of the related tasks tobe performed by the operator or maintainer of theequipment,

b. the position of the body during performance of operationsand maintenance tasks,

c. mobility and flexibility demands imposed by maintenancetasks,

d. the touch, grasp, torque, lift, and carry requirements of thetasks,



e. increments in the design-critical dimensions imposed byclothing or equipment, packages, and tools, and

f. increments in the design-critical dimensions imposed bythe need to compensate for obstacles and projections.

14.3.2 Static bodycharacteristics

R 14.3.2.1 Static data. Exhibit 14.3.2.1 presents static humanphysical characteristics and measurement values which should beused, as applicable, in design problems. Exhibit 14.3.2.1addresses the following body parts: head, seated body, standingbody, and hands.

P 14.3.2.2 Relevant static anthropometric data. If applicable,designers and human factors specialists shall use the relevantanthropometric design criteria and guidelines from this guideassociated with:

a. hand and finger access in section 6 (see paragraphs6.4.3.2, 6.4.3.3, and 6.4.3.4),

b. handle features for lifting and carrying in section 6 (seesections 6.2.5.2 and 6.2.5.3),

c. spacing between controls in section 7 (see paragraphs7.4.3.1, 7.4.4.10.1, and 7.4.4.11.1), and

d. common working positions in section 9 (see paragraph9.4.1).



14.3.3 Dynamic(mobile) bodycharacteristics

This section presents: (1) information concerning the range ofwhole body motion characteristics, and (2) design guidelines anddata on joint and body motion. Where such data are in othersections with application topics such as design for maintenanceand workplace design, cross references are provided.

14.3.3.1 Range ofwhole body motion

Efficiency and accuracy of task performance can be maintainedonly if required body movements are within safe and comfortablelimits. Human variability in range of body and joint movement isattributable to many factors, including the following:

a. Age becomes a factor after age 60, at which time mobilityhas decreased 10 percent from youth.

b. Sex differences favor greater range in females at all jointsexcept the knee.

c. Body build is a significant factor. Joint mobility decreasessignificantly as body build ranges from the very slender,through the muscular, to the obese.

d. Exercise increases movement range. Weight training,jogging, and the like may tend to shorten certain musclegroups or increase their bulk so movement is restricted.



e. Fatigue, disease, body position, clothing, and environmentare other factors affecting mobility.

This section provides introductory definitions related to theangular motion of skeletal joints. Knowledge of the range ofjoint motion helps the designer determine the placement andallowable movement of controls, tools, and equipment.

P 14.3.3.1.1 Trunk movement. Workplace designs based upondesign-driven body positions shall allow enough space to movethe trunk of the body. The design shall be based upon:

a. the required tasks and human functions,

b. the need for optimal positions for applying forces, and

c. the need for comfortable body adjustments andmovements.

P 14.3.3.1.2 Whole body movement. If large forces that are greaterthan 13.6 kg (29.98 lb) or large control displacements that aremore than 380 mm (14.96 in) in a fore-aft direction are required,the maintainer shall be given enough space to move his or herentire body.

14.3.3.2 Joint motion Joint motion capabilities make body movements possible. Jointmovement is measured at the angle formed by the long axes oftwo adjoining body segments or at the angle formed by a bodysegment and a vertical or horizontal plane. The total range ofmotion is measured between the two extreme positions of thejoint The types of movement are defined below and areillustrated in exhibits which follow.

Definitions. Abduction is movement away from themidline of the body. Adduction is movement toward themidline. Circumduction is a continuous circularmovement of a limb. Depression is the lowering of abody member from its normal position. Elevation is theraising of a body member from a normal position.Extension is the straightening of a limb or an increase inthe angle between parts of the body. Flexion is theprocess of bending a limb or decreasing the angle betweenparts of the body. Lateral rotation is turning away fromthe midline of the body, while medial rotation is turningtoward the midline of the body. Pronation is thedownward turning of the palm, or lying face down andsupination is the upward turning of the palm, or lying faceup.

P 14.3.3.2.1 Single joint movements. Designers and human factorsspecialists shall use the data in exhibit 14.3.3.2.1 for designproblems involving the movement of a single joint. This exhibitpresents single joint movement ranges for males and females.



P 14.3.3.2.2 Range of motion for two joints. Exhibit 14.3.3.2.2shall be used for design problems involving the motion of twojoints. Designers shall avoid using single joint movement datafor adjacent joints because they are usually not additive.

Discussion. The range of joint movement is drasticallyreduced by movement of the adjacent joint. Exhibit14.3.3.2.2 defines the change in range of motion of a



given joint when complemented by movement of theadjacent joint.

Example. The following illustrates how exhibit14.3.3.2.2 is to be used. The first entry is read: theaverage shoulder has a full range of extension of 59.3degrees with the elbow in a neutral position (locked inhyperextension). When shoulder extension was measuredwith the elbow flexed to one third of its full jointmovement range (these movements can be determinedfrom illustrations six and seven in the previous exhibit),the mean value of shoulder extension was found toincrease by 1.6 degrees, or approximately 103 percent ofthe base value. The results for other movements andadjacent joint positions are presented in a similar manner.

P 14.3.3.2.3 Design limit approach. The design limit approach,which concerns the selection of correct percentiles for the designsolution and which is prescribed in section 14.1.2 shall be applied



to design issues concerning the range of motion of singular andmultiple joints.

P 14.3.3.2.4 Use of this guide’s dynamic data. Designers andhuman factors specialists shall use the dynamic anthropometricand biomechanics guidelines found throughout this guide whereapplicable to dynamic tasks. They shall obtain data for criticaldynamic task that are unique to the system mission. These datamay be obtained from other appropriate anthropomety sources orfrom appropriate measures on a suitable sample.

Examples, though not an exhaustive list, of additional data fromother sections of the guide that have some basis in user mobilityand general task dynamics are:

a. mobile work space dimensions in section (see paragraph9.4.2.2),

b. visual line-of-sight and optimal display and control zonesin sections 7 and 9 (see paragraphs 7.2.1.6.3, 7.2.1.6.8,9.5.4.2, and 9.5.4.4),

c. whole body access and passageways in section 9 (seeparagraphs 9.3.1.1 and 9.3.4.6),

d. seated and standing workstations and consoles in section 9(see paragraphs 9.4.3.1, 9.5.1.1, and 9.5.4.4), and

e. visual display terminals in section 9 (see section 9.6).

Discussion. Most dynamic tasks will be system specific.Critical tasks are those whose efficient performance iscritical to the mission and to the safety of users, system,facility, or equipment.

14.4 Reach Reach limits are clearly dependent on the task, motion, andfunction to be accomplished by the reach action. Limited reachdata on standard anthropometric positions are available in sourcesof static and dynamic anthropometric data. Reach envelopesneed to be constructed for actual working positions and forexplicit design purposes. Reach envelopes may be related to abody reference point (such as the shoulder joint), to ameasurement apparatus point, or to a design point (such as a seatreference point). This section provides design criteria andguidelines for using reach data and constructing reach envelopes.

P 14.4.1 Task and body position effects. The following taskconsiderations shall be taken into account in order to establishreference points and to obtain the reach information needed toconstruct a reach envelope:

a. the nature and requirements of the task to be performed(see also paragraphs 14.3.1.2 and 14.4.4 for the nature ofthe reach task),



b. body position while reaching (standing, seated, seat backand seat pan angles, and others),

c. whole body movement capabilities and restraints (seatbelts, harnesses, necessary and permitted movements ofthe torso),

d. design purposes such as: to accommodate the appropriateportion of the population, to enhance task performance,orto avoid striking reachable surfaces, and

e. equipment locations that interfere with reach, vision orintercommunications.

R 14.4.2 Reach envelope data collection. Designers and humanfactors specialists should understand that reach envelopemeasurement data are often related to the data collectionprocedures and apparatus. Often data can be found or should becollected to relate the design reference point of concern to thereach capabilities of the actual users. Another factor in datacollection is the amount of whole body movement allowed. Forexample, consider bending the torso forward so that one or bothshoulders no longer touch the seat back.

Example. Exhibit 14.4.2 shows an example in whichreach measurement is related to the seat reference pointfrom a restrained shoulder level. In the left graph, a sideview reference plane is shown, and in the right graph, atop view is shown in terms of reach angles. All measuresand dimensions are relative to the apparatus.

Exhibit 14.4.2 Reach envelopes in vertical and horizontal planes

Discussion. An issue surrounding the application of reach data ishow to relate static anthropometric reach dimensions, shoulder



joint points, data collection procedures and apparatus referencepoints, and design reference points. Most reach measurementsare made relative to an apparatus reference point. A furthercomplication is that the apparatus and design seat reference pointmay not be the same or might not reflect the same seatconfigurations (back and pan angles).

Definition. Seat reference point is a point in the mid-sagittal plane where the seat back and seat pan intersect.

P 14.4.3 Reach envelopes for control actions. Reach envelops forcontrol tasks shall be bassed upon 5th percentile female reachdata co as to accommodate at least 95 percent of the population.

P 14.4.4 Reach envelope interaction with the reach task. Reachenvelope data shall be collected or modified for the tasks,motions, or functions to be accomplished by the reach. Exhibit14.4.4 (a) defines some task demands (touch, grip, and grasp) thataffect reach characteristics and measures.

Exhibit 14.4.4 (a) Touch, grip, and grasp functions and interactwith arm reach

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Exhibit 14.4.4 (a) (continued) Touch, grip, and grasp functions thatinteract with arm reach

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Discussion. Fingertip touch results in the largest reachdimensions appropriate for touch controls. Other graspfunctions would reduce the reach envelope. Two handedoperations, greater precision, and frequent or continuousoperation would necessitate locating the task closer to thebody. Bulky clothing could affect reach capabilities.

Examples. Exhibits 14.4.4 (b) and (c) present 5thpercentile female reach envelope data as examples of onepossible presentation for such data. The data representright hand reach for a fingertip grasp task. In exhibit14.4.4 (b) horizontal contours are shown at the 46 and 61cm levels.

Exhibit 14.4.4 (b) Thumb and forefinger grasp boundary data for females in the 46 cmand 61 cm horizontal planes



In exhibit 14.4.4 (c) vertical planes are shown for the 0and -15 cm planes. For design use, data would bepresented for other horizontal and vertical planes. Forthis example, shoulders were restrained against the seat.

Exhibit 14.4.4 ( c) Thumb and forefinger grasp boundary data for females in the 0 and -15cm vertical planes

Three factors can affect three-dimensional reachenvelopes: the effects of different hand manipulationtasks, the effects of permitting torso and shouldermovement, and the effects of the seat back angle of thedata collection apparatus. For instance, the exhibit showsthumb and forefinger grasp. Not shown is that fingertiptouch reach would increase by 7.0 cm (2.8 in) and full



hand grasp reach would decrease by -5.5cm (2.2 in) fromtheir fingertip grasp reach values.

Additional data also not shown in the exhibit reveals thatif the seat back angle were changed from 13 degreesrearward (as shown in the exhibits) to the verticalposition, that is to 90 degrees, then reach measures in ahorizontal plane from 0 degrees (arm straight forward andhorizontal) to 90 degrees to the right increase as follows:

a. at 0 degrees, by 1.02 cm (.40 in);

b. at 15 degrees, by 1.27 cm (.50 in);

c. at 45 degrees, by .94 cm (.37 in);

d. at 60 degrees, by .66 cm (.26 in); and

e. at 90 degrees, by .25 cm (.10 in).

R 14.4.5 Strength or fine manipulation. Tasks which requirestrength or fine manipulation, as well as repetitious tasks shouldbe located well within the perimeter of the reach limit envelope.

Discussion. The strength that can be exerted variesconsiderably throughout the reach envelope. As wasnoted in the previous example, the reach envelope varieswith the type of grasp required in defining the envelope.This rule points out that one may need to furtheraccommodate the task location by the strength, finemanipulation, or repetitive nature of the tasks to beperformed. In these cases, consider the capabilities of thesmall (5th or 1st percentile ) female user and alsoprovide sufficient space and adjustability to accommodatethe large male.

14.5 Humanstrength andhandlingcapacity

The designer and human factors specialist need to know thelimits and ranges of human strength to create designs that arewithin the capabilities of potential users. If demands on humanstrength are too high, inefficient and unsafe worker performancewill result. If the designer underestimates strength, unnecessarydesign effort and expense may be incurred.

This section introduces muscle strength factors, and providescriteria and guidelines on control forces, as well as push and pullforces. This section also provides supplemental criteria andguidelines on lifting and carrying.

14.5.1 Musclestrength factors

The forces delivered by the human body depend on thecontractile strength of the muscles, and the mechanicaladvantages of the body lever system with the joints serving asfulcra and the long bones serving as levers.

Knowledge of some of the many factors that relate to muscularstrength may aid design personnel in understanding human



physical capabilities. In addition to the strength capabilities ofvarious body members, other factors include: (1) age, (2)endurance, (3) gender, (4) body build, (5) body position, (6)handedness, (7) exercise, (8) diet and drugs, (9) diurnal variation,and (10) emotional and fatigue states. Gender and handednessare discussed below while strength limit factors are presented inthe criteria and guidelines throughout section 14.5.

Discussion. In general, females are about 35 to 85% asstrong as males with varying differentials for variousmuscle groups. Gender differences favor greater range injoint motion in females at all joints except the knee. Thepreferred hand and arm are approximately 10% strongerthan the non-preferred hand and arm.

Definitions. There are three basic categories of strength:(1) static strength, also known as isometric strength,which is steady force exerted while the limbs are in astationary or static position, (2) dynamic strength, whichis a force exerted by limbs moving in a smooth mannerover time, such as while lifting an object, and (3)explosive strength, which is the application of peakamounts of strength for short periods of time, usuallyperiodically, such as in running or sprinting.

14.5.2 Exertedforces

R 14.5.2.1 Maximum young male force or resistance for acontrol. The maximum amount of force or resistance designedinto a control should be determined by the greatest amount offorce that can be exerted by the weakest person likely to operatethe control. Control force limits, like most strength design limits,should be based upon the 5th percentile (or, for critical tasks, the1st percentile) of the female user population. Female strengthdata when it becomes available will be included in MIL-HDBK-759B.

Exhibits 14.5.2.1 (a) and (b) represent 80% of the maximumexertion forces for the 5th percentile male for the arm, hand andthumb. Since the experimental conditions used to collect thesource data yielded maximum possible exersion values for youngmen, these values are were too high for design purpose. Fordesign, one does not want to deliberately or consistantly requiremaximum exercisions. Thus these source values were reduced by20% before applying them as design criteria. Male data shouldbe selected based upon the body components involved in thespecific exertion task. To estimate female strength, male datashould be further reduced according to paragraph 14.5.2.4.Females can apply most strength when torso, back, and legs aremajor contributors. Female upper body and arm strength areweakest (see also comparative lifting strength informationparagraph 14.5.2.4 and 6.2.5.1.5).

Discussion. The maximum force that can be applied willdepend on such factors as the type of control, the bodymember used to operate it, the position of this body



member during control operations, the general position ofthe body, and whether or not support is provided bybackrests.

Exhibit 14.5.2.1 Male muscle strength of the arm, hand, and thumb for control forces (5thpercentile values)

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Exhibit 14.5.2.1 (continued) Design criteria for male muscle strength of the arm, hand, andthumb for control forces (5th percentile values)

P 14.5.2.2 Increasing strength values. Strength values shall beslightly increased if:

a. a lifting yoke or other special harness is to be used,

b. the object is unusually easy to handle,

c. the required force must be applied infrequently or only fora few seconds, if more than one per 30 seconds, decreaseby .30 or

d. the working body parts are provided with suitable support.

P 14.5.2.3 Decremented strength values. Strength values shall bedecremented if:

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a. the object is very difficult to handle (for example, bulkyor slippery),

b. access and work space are less than optimum,

c. the required force must be applied continuously for morethan one minute (strength decreases after 5 seconds), ifmore than once per 30 seconds decrease by 30 per cent.

d. the object must be finely positioned or delicately handled,or

e. the task must be performed repeatedly.

R 14.5.2.4 Comparative strength. Research has produced littleinsight into the strength of women relative to men. New femalestrength data are to be added to MIL-HDBK-759 in the nearfuture. The following strength relationships developed by the USArmy Research Institute of Environmental Medicine should beused until better data becomes available:

a. For upper extremities, females strength is 56.5% of men.

b. For lower extremities, female strength is 64.2% of men.

c. For trunk extremities, female strength is 66.0% of men.

Explanation. These numbers may serve as a designguideline until more information becomes available.

R 14.5.2.5 Preventing tremor in positive control performance.Tremor is important in activities in which a body member ismaintained in a precise position or motion (tasks involving finecontinuous control, detailed drawing, tracking, tracing, cutting, orpainting). The following features should be designed intosystems or equipment, where applicable, to help reduce tremorand ensure positive control performance of fine detailed tasks:

a. ensure that visual reference can be used,

b. provide support of the body and the member involved, forexample, the hand or arm,

c. support the hand because tremor is less if the hand is203.2 mm (8 in) above or below the heart level, and

d. provide mechanical friction in the control device to addenough resistance to movement to partially counteract theenergy of the vibrations of the body member.

Definition and discussion. Tremor is the oscillation of abody extremity which may occuring along with an effortto maintain a fixed position or direction. The degree oftremor is measured by the distance or number ofdepartures from the fixed path or position per unit oftime. Tremor increases when (1) effort is made not to



tremble, and (2) fatigue is present. It is greatest in verticalmotion, less in front-to-back motion, and least in side-to-side motion.

14.5.3 Push andpull forces

R 14.5.3.1 Horizonal direction of force. Manual horizontal pushand pull forces that are initially necessary to set an object inmotion, or to sustain the motion over a period of time, should notexceed the values given in exhibit 14.5.3.1. For the second orthird person applying horizontal forces, the value in the exhibit’sfirst column should be doubled or tripled, respectively. For eachadditional person (beyond the third) another 75 percent of theforce value in the first column should be added.

Explanation. The exhibit shows maximum push and pullforces that a designer would be expected to use whenappropriate body positions, support, and tractionconditions are provided. Use of the maximum valuesshown in the exhibit is predicated upon a suitable surfacefor force exertion (vertical with rough surfaceapproximately 400 mm (15.75 in) wide and between 0.51- 1.27 m (1.673 - 4.167 ft) above the floor) to allow forceapplication with the hands, shoulders, or back.



R 14.5.3.2 Vertical direction of force. Required manual verticalstatic lift forces, should not exceed the applicable 5th percentilepeak or mean force values given in exhibit 14.5.3.2.

Explanation. Based upon recent experience withinNIOSH the forces found in the source which studiedyoung military personnel has been reduced by 20 percentin exhibit 14.5.3.2. The mean forces given representforce over a three second interval, beginning two secondsafter it reached a minimum value of 45 N provided that itcontinued to exceeded this minimum. Exhibit 14.5.3.2reflects the higher of two trials for each condition.

P 14.5.3.3 Forces for handles. Designers shall use the forcecriteria for handles cited in section 6 (see paragraph 6.2.5.1.5).



14.5.4 Lifting andcarrying

There are three major muscular components of weight-lifting: (1)the legs, (2) the arms-back, and (3) the arms. In efficiently liftingobjects to different heights, these components are combined indifferent ways. Specifically, lifting objects to about knee heightinvolves primarily the use of the leg component, while objectslifting to about waist level involves a combination of leg andarm-back components. Lifting objects to shoulder level or higherrequires the use of all three components.

P 14.5.4.1 Lifting and carrying limits. Data, criteria, andguidelines in section 6.2.2 shall be used to establishrecommended maximum weights to be lifted and carried by oneand two people. (See sections 6.2.5.1 and 6.2.5.3 for handle useand dimensions in relation to weight limits).

14.6 Design forphysical comfort

Like thermal comfort in section 13, physical comfort may bedifficult to quantify but people can perceive and expressdiscomfort. In the physical comfort area, discomfort can becomepainful or result in chronic disorders. Usually there arephysiological bases for discomfort. Factors that can influenceperceptions of comfort and discomfort include: (1) physical andphysiological condition, (2) fatigue, (3) working conditions andstress, (4) provisions for physical support, (5) impediments orrestraints to movement, and (6) environmental conditions.

P 14.6.1 Adjustment capabilities. Designers and human factorsspecialists should provide appropriate adjustment capabilities inworkspace design (seating, body part support, and task location)that permit individuals to easily and safely adjust workspacedimensions to their preferred body positions and task locations.Such adjustability should be achieved by:

a. using the design limits method to accommodate the rangeof the population distribution between the 5th and 95thpercentile statistics,

b. considering the practical variations in task locationswhich may be preferred by the workers, and

c. considering the frequency and duration of tasks andemphasize adjustment of the most important, frequent,and long duration tasks.

R 14.6.2 Restrictions to movement. Designers and human factorsspecialists should avoid design features that unnecessarily restrictthe individual worker’s ability to make frequent posturaladjustments. If possible, postural adjustments should be feasibleand safe without interruption of the tasks.

Discussion. The concept of individualized form fittingseats may be appropriate for astronauts but such formfitting may be too restrictive for postural adjustmentsneeded for most work. If fit or barriers to comfortablemovement cause constant adjustments for comfort orbalance, the additional muscular effort to attain comfortmay contribute to muscular fatigue.



R 14.6.3 Body support. Body part supports should be appropriateand compatible with the tasks. Necessary padding compositionshould be provided to accommodate soft tissue and bonyprotuberances without impeding motions or resulting inirritations.

P 14.6.4 Body posture. Design features shall not require awkwardbody positions for operators or maintainers. Tasks that requirephysical exertions shall permit a range of comfortable posturesappropriate for safe application of the required forces ormovements.

P 14.6.5 Demands upon tasks. Designs and design-driven tasksthat could over time cause repetitive movement disorders or thatrisk back, neck, shoulder, wrist discomfort, stress, or injury shallbe formally identified by the contractor and be reviewed by theacquisition program office. Those designs and tasks that arequestionable shall be reviewed for potential equipment and taskdesign changes or redesign. Tasks that could require specialpersonnel selection for physical attributes, or special work-restrequirements shall be identified and reviewed for potentialequipment and task redesign.

section 14 contents 14 anthropometry and · pdf filehfdg section 14 contents january 15, 1996...

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