OCCUPATIONAL ERGONOMICS Chapter 3 ANTHROPOMETRY AND PHYSICAL ERGONOMICS

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OCCUPATIONAL ERGONOMICS Chapter 3 ANTHROPOMETRY AND PHYSICAL ERGONOMICS

OCCUPATIONAL ERGONOMICS Chapter 3 ANTHROPOMETRY AND PHYSICAL ERGONOMICS

ANTHROPOMETRY AND PHYSICAL ERGONOMICS Learning Objectives At the conclusion of this chapter, learners will

ANTHROPOMETRY AND PHYSICAL ERGONOMICS Learning Objectives At the conclusion of this chapter, learners will be able to do the following: n Demonstrate working knowledge of anthropometric methods n Demonstrate ability to utilize anthropometric data in a design scenario n Describe various factors that can affect anthropometric measures n Demonstrate working knowledge of human strength attributes n Describe various factors that can affect human strength 2

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) Some Key Terms Anthropology: The science of human

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) Some Key Terms Anthropology: The science of human beings. n Physical Anthropology: The study of physical characteristics of human beings. n Anthropometry: A branch of physical anthropology dealing with body dimensions and measurements. n 3

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) DIVISIONS OF ANTHROPOMETRY 1. 2. 3. Static anthropometry:

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) DIVISIONS OF ANTHROPOMETRY 1. 2. 3. Static anthropometry: Body measurement without motion (e. g. , stature). This measurement helps the designer "fit" the worker into the workplace. Dynamic anthropometry: Body measurement with motion (e. g. , vertical reach envelopes). This measurement helps the designer check if worker can "function" within the workplace. Newtonian anthropometry: Body segment measures for use in biomechanical analyses (e. g. , link lengths, center of mass, inertial characteristics). 4

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) SOURCES OF ANTHROPOMETRIC DATA 1. Military (U. S.

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) SOURCES OF ANTHROPOMETRIC DATA 1. Military (U. S. and others) 2. U. S. Public Health Service 3. British Office of Population Censuses and Surveys (OPCS) 4. Other national-based surveys 5. Industrial labs. 5

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) FACTORS AFFECTING BODY DIMENSIONS 1. Human variation due

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) FACTORS AFFECTING BODY DIMENSIONS 1. Human variation due to: - Age Gender Ethnic origin Long-term population shifts 2. Personal equipment and clothing 6

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) USE OF ANTHROPOMETRIC DATA 1. Design for the

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) USE OF ANTHROPOMETRIC DATA 1. Design for the individual: Best design, but can be expensive. 2. Design for adjustable range • 5 th percentile to 95 th percentile of the user population • Preferred for multiple users, but can be expensive also • Make special accommodation for those outside range 3. Design for population extremes • For smaller female (5 th percentile) OR larger male (95 th percentile) • Door frame, shelf height, etc. 4. Design for population average • Normally not recommended • Public facilities • Recommended only when used for a short duration 7

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ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) Evaluating Anthropometric Design Parameters From Standard-Normal statistical distribution

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) Evaluating Anthropometric Design Parameters From Standard-Normal statistical distribution (bell curve): Z = (x - µ)/σ (Eq. 3 -1) where, Z = standard normal value corresponding to population cumulative density µ = average, or mean of dimension for population σ = standard deviation of population x = value of measured dimension 10

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ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) Analysis/Design Objectives 1. Determining design specification values. 2.

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) Analysis/Design Objectives 1. Determining design specification values. 2. Evaluating population accommodation. Summary of General Design Procedures Step 1. Select anthropometric measure(s) that directly correspond to the required engineering and/or architectural design specification. 12

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) Engineering Specifications Display Height Anthropometric Measure/Reference Eye Height

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) Engineering Specifications Display Height Anthropometric Measure/Reference Eye Height Console Height (undersurface) Tool Handle Size Knee Height Hand Width, Length, etc. 13

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) Step 2. For each matched pair identified in

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) Step 2. For each matched pair identified in Step 1, determine whether the design must fit a singular population percentile, or a range along that dimension. Step 3. Apply any necessary correction factors. Step 4. Combine all selected design specifications into a “model” and check for feasibility. 14

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) MUSCULAR STRENGTH Strength is defined as the ability

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) MUSCULAR STRENGTH Strength is defined as the ability of a muscle group(s) to generate maximal voluntary torque about a joint. A key word in this definition is “voluntary, ” as strength data is collected using protocols designed to elicit subjective (e. g. , psychophysical) responses. Typically then, the phrase “maximum voluntary contraction” (MVC) is used to describe the response recorded by an external instrument during a strength testing protocol. 15

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) FACTORS AFFECTING MUSCULAR STRENGTH 1. Biological and personal

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) FACTORS AFFECTING MUSCULAR STRENGTH 1. Biological and personal factors • • • Age Gender Body composition Hand preferences Biomechanical factors (mechanical advantage) Ethnic origin Fatigue Exercise Diet, overall health 16

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) 2. Environmental factors • • Altitude Acceleration 3.

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) 2. Environmental factors • • Altitude Acceleration 3. Psychological factors • • Motivation Emotional state 4. Occupational factors • • Task characteristics - posture, coupling, duration, frequency, etc. Clothing and personal equipment 17

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) Hand Strength § § - Grip - Pinch

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) Hand Strength § § - Grip - Pinch § § § Lateral (Key) Chuck (three fingers), and Tip In occupational setting, hand force can be broadly classified into “Power” and “Precision” 18

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ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) TYPES OF MUSCULAR CONTRACTION 1. Static Contraction Isometric

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) TYPES OF MUSCULAR CONTRACTION 1. Static Contraction Isometric • • contraction where the muscle does not change length no external work done, energy spent, fatigue sets in quickly example: pushing against a wall 21

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) TYPES OF MUSCULAR CONTRACTION (contd. ) 2. Dynamic

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) TYPES OF MUSCULAR CONTRACTION (contd. ) 2. Dynamic Contraction Isokinetic • • contraction of muscle at constant velocity normally associated with external resistance being measured at constant velocity, rather than muscle fibers proper example: peak force measured of arm curl at 30 deg/sec velocity using Cybex machine 22

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) Isoinertial • mass constant, but velocity and muscle

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) Isoinertial • mass constant, but velocity and muscle length change, tension not constant. example: lifting a constant weight Isotonic • • contraction where the muscle shortens but the tension remains constant work done, energy spent example: holding barbells 23

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) RANGE OF JOINT MOTION Range of motion is

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) RANGE OF JOINT MOTION Range of motion is defined as the maximal angle range between two body segments, or between a body segment and reference plane, measured about a common joint. FACTORS AFFECTING RANGE OF JOINT MOTION Age Body composition Regular exercise Fatigue Biomechanical factors Gender Occupation Ethnic origin Dominant, non-dominant side of body Clothing and personal equipment 24

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ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) Bio-instrumentation To measure body segment lengths, a set

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) Bio-instrumentation To measure body segment lengths, a set of anthropometric calipers is used. A handgrip dynamometer (Jamar or Lafayette) is used to measure handgrip strength and a pinch dynamometer is used to measure pinch strength. The protocol used to measure has been discussed earlier. 26

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) CASE STUDY 3 -1. Evaluating Population Design Parameters.

ANTHROPOMETRY AND PHYSICAL ERGONOMICS (CONTD. ) CASE STUDY 3 -1. Evaluating Population Design Parameters. (Page 41) CASE STUDY 3 -2. Evaluating Population Accommodation. (Page 42) 27