26 ANTHROPOMETRY, PRINCIPLES, MEASUREMENTS, APPLICATION OF ANTHROPOMETRY IN ERGONOMICS AND DESIGN

Geetha Suresh

1.0 Introduction

Dear Students, you must be wondering what is this Anthropometry and measurements? In nutrition based courses, we would have used the height and weight of individuals for the BMI and other purpose, but for a design paper, how does this concept related?

The comfort of Human being to sit, stand, eat, walk freely, work without stress you need to understand the basic anthropometric measurements, the principles and its relation to ergonomics and designing theories.

The Anthropometric measurements are most important data for the Interior Designing concepts, furniture designing, space layouts.

2.0 Objective of the Module:

1. The student should be able to understand the anthropometric principles and how to measure the data.

2.The module aims at relationship between the anthropometry and ergonomics in design

3. A thorough understanding of application of anthropometry at various stages

3.0 The Impact of Human Factors, Ergonomics & Anthropometry on Design:

A designer can use anthropometric data, application of ergonomics and human factors to their advantage or otherwise these things may work against their design ideas.

Good design always observes these factors first because no one wants to use or own a product or service which carries out the task inappropriately or poorly or even dangerously.

Consider the following….

If a Toilet designed by a fashion designer, then the consequences of the design:

• As it’s known that Fashion designers work to a fantasy of what the human body looks like or they imagine looking like. They are taught to draw human figures in a different, idealized way.
• The two figures in the middle are typical of fashion design drawings. Designs are based on these oddly proportioned, unreal body shapes.
• If a product designer were to work using the same imaginary body shapes that fashion designers do, a typical toilet would look like this.
• None of us would willingly climb a stepladder every time we need to use our toilet.
• Any designer when designing the product or space or for that matter fashion clothing, should work on the comfort of the user.

Why should designers be aware of anthropometrics and ergonomics?

Designers must be aware of anthropometrics and ergonomics to ensure their ideas of end product or service is safe and especially while designing any public spaces they should be even more socially responsible and sensitive. The designers accommodate various percentiles of the population so that the vast majority of people can get a chance to use and interact with the designed products or service.

4.0 Meaning of Anthropometry:

The study of human body measurements on a comparative basis is known as anthropometrics. Its applicability to the design process is seen in the physical fitness, or interface, between the human body and the various components of interior space.

It is the measurement and study of human body dimensions like height, weight, reach lengths, eye heights, etc. It is one of the most important data sets applied to fit people with their products and physical environment.

There are two ways of measuring Anthropometry.

A) Static Anthropometry

The static anthropometric data is a basic set of numbered variables and brief descriptions of their use in ergonomics while the body is still.

Static measurements

• Measurements taken when body in a fixed state.
• Skeletal dimensions (between the centers of joints, i.e. between elbow and wrist). Contour dimensions (skin surface/head circumference).
• Body measurements vary as a function of age, gender, ethnicity (and nutrition, but not as clear).

B)Dynamic Anthropometry

The dynamic anthropometric data is a basic set of numbered variables and brief descriptions of their use in ergonomics while the body is moving.

Dynamic (Functional) Dimensions

·         Taken when body is engaged some physical activity

·         Body members function in concert

·         No systematic procedure for translating static into dynamic measurements

5.0 Anthropometrics and Design:

5.1 Design Limitations:

a. Myth of designing for the “average” person – since there are no people whose body dimensions are all at the 50th percentile. Body dimensions aren’t linearly correlated so people with short arms don’t necessarily have short legs, etc. While the use of the 5th and 95th percentiles on one body dimension may exclude 10% of the population, the use of these on 13 dimensions can exclude 52% of the population.

b. Myth that designing for 5-95th percentile – designing to include the ranges between the 5th and 95th percentiles of anthropometric data doesn’t fit everyone. There are two misunderstandings:

(1)   5 – 95 percentile is only 90% – 5-95% _ 95% of people, it’s only 90%! If you design for 90%, you’ll fit 9 out of 10, 90 out of 100, 900 out of 1000, etc.

(2)   Anthropometrics are based on population “norms” – must consider differences if dealing with a subpopulation such as a group of Southeast Asians or offices for a pro basketball team.

c. Use appropriate anthropometric data- anthropometric data are only specific to the populations which they describe. If the population is poorly specified the percentiles may be biased. Also, percentiles are only specific to the dimension which they describe.

(1)   Maximum value – Examples include door clearances and door widths for wheelchairs and users (arms must work the chair), getting a gurney through a door, and railings.

(2)   Minimum clearances – Examples include safety clearances for railings and elevator buttons.

d. Design for an adjustable range – but be cautious of the cost/benefits of including more percentiles. Each consecutive percent of the population to be accommodated increases the costs relative to the benefits, i.e. there are no diminishing returns.

5. 2 Design Aids:

a. Data tables – have anthropometric data but may be difficult to find and use.

b. Human scale – a series of templates are used by a computer to change relevant attributes as populations change. Values are printed. Unfortunately, it’s still necessary to draw the figures from the data values.

c. Mannequins – a two-dimensional drawing or figure which articulates like ADAM (Anthropometric Data Applications Mannequin) with plastic parts snap together like clear moveable paper dolls or overlay transparencies.

d. Models – three-dimensional models like “George” can be useful as examples of anthropometric data. Models have often been used by clothing manufacturers.

e. Computer generated models – three-dimensional models of a user at a specified percentile in certain respects. Can see elevation, plan, or perspective. An example is “SAMMIE”, System for Aiding Man-Machine Interaction and Evaluation. Image can be altered to simulate motion but we don’t have good data for most biomechanics.

5.3. Issues of Diversity:

A wide variety of factors influence human body dimensions, including the following categories. “Clinical normality” in height is defined as about the range 54″-79″. The average stature worldwide is 64.96″ ´3.15″ for men and 60.5″ ´2.95″ for women.

a. Ethnic differences– shortest people in the world are the Efe&Basua “pygmies” in Africa. There men are 56.61″ ´2.79″ for men and 54.01 ´3.07″for women. The largest are in southern Sudan, are the Dinka Nilotles with men at 72″ ´2.4″ and women at 66.49″ ´2.28″. The smallest living person is 29 1/2″, a male Portuguese professional drummer. The smallest person ever recorded was a Dutch woman at 23.2″ tall (1876-1895). The tallest living person is a Pakistani male at 94.09″ tall. The tallest ever recorded was an American man at 107 1/2″ tall (1918-1940). (He had to eat ~ 8000 calories per day).

(1) Sitting height – Stature differences become reduced when sitting down.

Sitting height – relative sitting height = sitting height ~ 53%stature

Different ethnic groups have different physical characteristics. Black Africans have proportionally longer legs than Europeans. Eastern people (Asians) have comparably shorter lower limbs. This is most pronounced for Japanese and less so for Chinese, Koreans, Thai’s, and Vietnamese. However, there is some evidence that this situation is changing and that Japanese youth have proportionally longer legs and wider faces.

(2) General rules – Two general rules have been developed which apply to ethnic differences.

(a)  Bergman’s rule – the body size of varieties increases with decreasing mean temperature of the habitat. Example: the ideal shape to be in the Arctic is a sphere.

(b) Allen’s rule – the relative size of exposed portions of the body decreases with decreasing temperature, i.e. nose, ears, toes, extremities will be proportionately smaller.

b. Body shape – soft tissue varies in shape and these variances may create differences in clearance and mobility requirements.

1) Mesomorph – body shape larger in the middle.

2) Ectomorph – very slender.

3)  Endomorph – overweight or pregnant with a wider body overall.

c. Sex differences – have key ergonomic consequences and separate data is usually used for men and women.

(1)   Dimensions – Men exceed women in all linear body dimensions except hip breadth. The lengths of upper and lower limbs are totally and consistently greater in men than women except for buttock-knee length. Women exceed men for skinfold thickness.

(2)    Soft tissue distribution – generally, fat is a greater proportion of body weight in women than men. Women have more fat content as subcutaneous fat in breasts, hips, thighs, and upper arms. Abdominal fat tends to accumulate below the navel in women and above the navel in men.

d. Growth and development – rates are very fast for children but decrease with age.

(1)   Children – At birth, average weight is 7.26lb ´.88lb and average height is 19.7in ´.8in. Trunk is 70% of body length at birth but only 52% of adult stature. Girls reach 50% of adult height before 2 years of age. Boys do the same at around 2 years of age. From birth to 20 years of age the body length increases 3-4 times and weight increases 20 times.

(2)    Adolescents – Related with puberty, boys begin a growth spurt from around 11.5 years of age which lasts until around 14 years of age. Girls spurt starts earlier, at around 9 years of age. It reaches its greatest rate around 12 years old and is completed by around 16 years of age. While height is changing, relative body proportions are changing as well.

e. Age group and Stature Considerations– It’s important to consider whether children or elderly people are included in anthropometric data.

(1)Height – Average heights of adults in the UK and US gradually decline with age after 20 years of age. Around 40 years of age most people begin to shrink in stature. Women shrink more than men and shrinkage accelerates with age.This shrinkage occurs in the intervertebral discs of the spine, possibly causing rounding of the back. Some reduction in height may result from shrinkage of lower limbs around the joints.

(2)Weight – The mean weight of adults increases from ages 20-45. From age 50 onward men’s weight declines. From age 60 onward women’s weight declines. Until 55 years of age, weight increases for taller people and there is an increase in hip breadth. Fat is rearranged from subcutaneous areas to deeper positions especially around abdominal organs. Lean body weight decreases with age as muscleswither. There is a decrease in muscular strength,however the mechanical tensile breaking strength of bone, muscle, and connective tissue decreases with age.

f. Disabilities– Worldwide, an estimated 400 million people manage with physical disability. In the US in 1970 69 million citizens had some physical disability. 5.4 million were visual problems, 20.1 million auditory problems, 18.3 million arthritis, and 7 million with mobility problems (.5 million wheelchair users). There is very limited anthropometric data.

(1)   Wheelchair Users – Chair bound people actually suffer three limitations:

(a) Condition which necessitates wheelchair use.

(b)   Lower eye-level – eye-level is 15 to 16 inches below that of most standing people and the seated posture also influences reach, controls, and access.

(c)    Possession of a cumbersome, awkward, space-consuming, distinctive and inelegant vehicle. While a standing person occupies 25in by 15in of floor space, requires 16in to 26in aisle width and can turn on the spot, a wheelchair user occupies up to 57in by 25in of floorspace, requires minimum aisle clearance of 31.5in and needs a turning circle of between 59in and 67in.

g. Pregnancy– Later stages of pregnancy decreases in the ability to lift, bend, reach, stand or walk for long periods, turn head, etc. so it is a form of temporary disability. Assuming a 0.02% pregnancy rate and 50,000,000 women of childbearing age, means an estimated 1,000,000 pregnant women at any time. Only recently have anthropometric surveys of pregnant women begun to be conducted (in Japan).

h. Time of day– Because the cartilaginous discs of the spinal column get compressed by body weight throughout the day we tend to be slightly shorter in the evening. Additionally, extremities (like feet) swell throughout the day, making them puffier in the evening.

6.0Statistical Treatment of the Anthropometric Data:

Designing for a single person demands his dimensional variations to be well accommodated. When designing for the use of the majority and for unknown individuals, one of the most relevant statistical interpretations and considerations is the percentile value of the collected data taken from a specific population group.

6.1What is Percentile?

Percentiles are the statistical values of a distribution of variables transferred into a hundred scale. The population is divided into 100 percentage categories, ranked from least to highest, with respect to some specific types of body measurements. The 1st percentile of any height indicates that 99% of the population would have heights of greater dimensions than that. Similarly, a 95th percentile height would indicate that only 5% of the study population would have greater heights and that 95th % of the study population would have same or lesser heights. The 50th percentile value represents closely the average which divides the whole study population into two similar halves with one half higher and the half with lower values in relation to the average value.

6.2Percentile Concept

It is the statistical value of a distribution of variables transferred to a hundred scale.

Ø  95th percentile: Only 5% of the population would have greater value

Ø   50th percentile: Represents closely the average

Ø   25th percentile: Only 25% of the population is within that value

6.3 When to opt for which percentile

Ø  Higher percentile: clearance e.g., door height, safety hatch, etc.

Ø   Lower percentile: access/reach e.g., door handle, grab rail, etc.,

Always, the basic thumb rules should be followed while designing:

•   Designing for the average

Ø   Typical/default (restaurant seating)

• Designing for the extremes

Ø   Doorways

Ø   Reach distances (controls)

• Designing for the range

Ø   Adjustability means to fit a wide range of individuals

Ø   5th percentile female to 95th percentile male

Ø   5’female to 6’2”male

Ø   Adaptability (most expensive but most preferred)

7 .0 Anthropometric Design Guidelines:

i) Use anthropometric tables appropriate for the population, & use data

ii)For special clothing, add appropriate allowances (winter jacket restricts reach by approximately by 2”

iii) Build full-scale mock-up of equipment/facility & use it w/user population

iv)Determine body dimensions important in design (sit height as basic factor in seat-to-roof in automobiles)

v)Define population to use the equipment/facilities

vi) Determine what principle should be applied (extremes, average or adjustable ranges)

vii) When relevant, select % of users served (90%, 95%) whatever is relevant to the problem

All the anthropometric data in the world cannot substitute for a full-scale mock-up.

7.1 Steps to apply Anthropometric data:

i) Select those anthropometric measures that directly relate to defined design dimensions. a. Examples: hand length related to handle size.

ii)For each of these pairings, determine whether the design must fit only one given percentile (minimal or maximal) of the body dimension, or a range along that body dimension.

   a. Examples: the escape hatch must be big enough to hold the largest extreme value of shoulder breadth and hip breadth, considering clothing and equipment worn;

iii) Combine all selected design values in a careful drawing, mock-up, or computer model to ascertain that they are compatible.

a.For example: the required leg-room clearance height, needed for sitting persons with long lower legs, may be very close to the height of the working surface determined from elbow height.

iv)Determine whether one design will fit all users. If not, several sizes or adjustment must be provided to fit all users.

a. Examples are: one extra-large bed size fits all sleepers; gloves and shoes must come in varied sizes; seat heights of office chairs are adjustable.

7.1.1 Use the following steps

Ø  Select measurements that relate to the design

Ø  Determine if design is to fit a certain percentile or a range

Ø  Combine values to ascertain compatibility

Ø  Determine if one design will fit all users

Ø  Anthropometry and personal space

7.1.2.Few Anthropometric design illustrations:

A door handle must not be lower than the highest standing knuckle height in a population so that all users can open the door without stooping

• The width of a chair must be no narrower than the hip breadth of a large woman
• The height of a doorway must be no lower than the stature of a tall person
• A door lock must be no higher than the maximum vertical reach of a small person.
• Seat heights and depths must not exceed the maximum height and buttock–knee lengths of small users

8.0 Summary:

• The anthropometric data, the principles followed and its applications in the design field are very essential for user friendly products and work place.
• The importance of anthropometrics helps the individual to be more safe and free from physical discomforts and fatigue.
• Any products, space design whether its commercial or residential need to be addressed with the anthropometric and ergonomic details into it, which eliminates the future discomfort and create a healthy living atmosphere to the human being.

Hope you could relate the needs of the anthropometric data and its importance, principles in the designing field. We will meet in the next modules with more in-depth information on ergonomics.

References:

1. Bridger, R. (2003). Introduction to Ergonomics (2nd ed). Taylor & Francis. London; New York.
2. Gandotra, V. & Patel, S. (2009). Women, Working Conditions and Efficiency. Oscar Publications. New Delhi, India.
3. Prevalence of Musculoskeletal Discomfort among Women Working in Khakhra Making Units, Roopa Rao, Online International Interdisciplinary Research Journal, {Bi-Monthly}, ISSN2249-9598, Volume-IV, Issue-I, Jan-Feb 2014