الصفحات الشخصية - what is...

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Islamic University of Gaza - Palestine

WHAT is ERGONOMICS


What ergonomics “does” can be summed up in three

questions:

• Who (Human) was it designed for?

• What (Task) was it designed for?

• What environment was it designed to function with?

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Steps to identify and anticipate ergonomic problems

1. Become aware of problem

2. Analyze task and conditions

3. Identify problem

4. State needs and goals

5. Select candidate solution

6. Engineering control or managerial control

7. Implement solution

8. Check success

Yes- problem solved now return to step 2 or 5


Six Pillars of Ergonomic Design “Wisdom”

1. User Orientation: Design and application of tools, procedures, and systems must be user-oriented, rather than just “task” oriented

2. Diversity: Recognition of diversity in human capabilities and limitations, rather than “stereotyping” workers/users

3. Effect on Humans: Tools, procedures, and systems are not “inert”, but do influence human behaviour and well-being

What is Ergonomics? “Wisdom”

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Six Pillars of Ergonomic Design “Wisdom”

4. Objective Data: Empirical information and evaluation is key in design process, rather than just use of “common

sense”

5. Scientific Method: test and retest hypothesis with real data, rather than “anecdotal” evidence or “good

estimates”

6. Systems: object, procedures, environments, and people are interconnected, affect one another, and do not exist

in “isolation”

What is Ergonomics? “Wisdom” (cont.)


Life-Cycle of Products, Procedures, and Systems

1. Initial Idea: driven by customers, technology change,

competitors, problems, needs

2. Requirements: user, manufacturer, standards,

government, cost, profit, marketing/sales

3. Concepts: design alternatives, comparison, choose best

one

4. Design: detail parts, integrating with rest of system,

prototype testing, optimization

What is Ergonomics? -Life-Cycle of Products-

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Life-Cycle of Products, Procedures, and Systems

5. Manufacturing: material, processes, assembly

6. Distribution/Sale: shipping, display, delivery, installation,

warranty

7. Use: security, safety, access, maintenance, repair

8. Disposal: toxicity, recycling, reusability, upgrade

What is Ergonomics? - Life-Cycle of Products- (cont.)


Biomechanics

“Biomechanics uses the laws of physics and engineering

concepts to describe motion undergone by the various

body segments and the forces acting on these body parts

during normal daily activities” (Frankel and Nordin, 1980)

Occupational Biomechanics

“Occupational biomechanics is …. the study of the physical

interruption of workers with their tools, machines, and

materials so as to enhance the worker’s performance

while minimizing the risk of musculoskeletal disorders.”

(Chaffin et al., 1999)

What is Occupational Biomechanics?

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Biomechanics – What is it?

• The mechanical bases of biological systems.

• The application of mechanical laws to living structures.


OCCUPATIONAL ERGONOMICS

& BIOMECHANICS

Biomechanical

Modeling Methods

Anthropometric

MethodsBioinstrumentation

Methods

Classifying and

Evaluating Work

Mechanical Work

Capacity

Evaluation

Methods

Kinesiology

Methods

Worker

Selection

Criteria & Training

Hand Tool

Design

Guidelines

Workplace &

Machine

Guidelines

Seating Design

Guidelines

Material

Handling Limits

Improved Performance &

Reduced Risk of Mechanical Trauma[Chaffin et al, 1999]

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Occupational Biomechanics

• Occupational Biomechanics is a sub-discipline within the general field of biomechanics which studies the physical

interaction of workers with their tools, machines and

materials so as to enhance the workers performance while

minimizing the risk of musculoskeletal injury.

• Motivation:

– About 1/3 of U.S. workers perform tasks that require

high strength demands

– Costs due to overexertion injuries - LIFTING

– Large variations in population strength

– Basis for understanding and preventing overexertion

injuries


Kinesiology – Is it the same as biomechanics?

• Kinesis (motion) + -logy (science, study of)

• Applied anatomy and mechanics

• Rasch & Burke (1978). Kinesiology

=anatomy (science of structure)

+physiology (science of body function)

+mechanics (science of movement)= science of movement of the human body.

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Kinesiology (cont.)

• Old (pre-1980) usage

– Title of a functional (applied) anatomy + biomechanics

course (“Kinesiology”).

• Continue to see that use

– many programs now put extra descriptors in the title for

clarification (e.g., “Anatomical Kinesiology”, “Functional

Anatomy and Kinesiology”).


Kinesiology (cont.)

• Current (post-1980) usage

– One of several terms used to characterize the discipline

or field (e.g., “Department of Kinesiology”).

• Other terms include “Exercise Science and Physical

Education”, “Exercise and Sport Sciences”, “Human

Movement Studies”, or “Movement Science”.

– Potentially an umbrella term for any form of anatomical,

physiological, psychological, or mechanical analysis of

human movement.

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Biomechanics: Does it exist in more than one field?

• Exercise and sport biomechanics

• Orthopedic biomechanics

• Occupational biomechanics

• Biomechanics of other biological systems


• Exercise and sport biomechanics

– improving athletic performance, reduction of athletic

injuries


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• Orthopedic biomechanics

– artificial limbs, joints, and orthoses to improve functional

movement capacity

– study of natural and artificial biological tissues



• Occupational Biomechanics

– Ergonomics and Human Factors

– reduction of workplace injuries


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• Biomechanics of other biological systems

– Comparative biomechanics (e.g., swimming in fish,

locomotion in apes)

– Equine (horse) and canine (dog) racing performance



What do we have in common?

• Application of fundamental mechanical principles to the

study of structure and function of living systems.

• Common measurement and analysis tools.

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Divisions of

Mechanics

(Bio)mechanics

Statics Dynamics Fluids

Kinematics Kinetics

Linear Angular

Deformable

Solids

Stress Strain


Why Study Biomechanics?

• From a mechanical perspective…

– How do we generate and control our movements?

– What mechanical and/or anatomical factors determine or

limit movement outcomes?

– How can we make our movements “better”?

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Problems (example)


Free-Body Diagrams

• Free-body diagrams are schematic representations of a

system identifying all forces and all moments acting on

the components of the system.

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2-D Model of the Elbow

From Chaffin, DB and Andersson, GBJ (1991) Occupational Biomechanics.

17.0 cm

35.0 cm

180 N

10 N

Unknown Elbow force

and moment


From Chaffin, DB and Andersson, GBJ (1991) Occupational Biomechanics. Fig 6.7

2-D Model of the Elbow

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Assumptions Made in 2-D Static Analysis

• Joints are frictionless

• No motion

• No out-of-plane forces (Flatland)

• Known anthropometry (segment sizes and weights)

• Known forces and directions

• Known postures

• 1 muscle

• Known muscle geometry

• No muscle antagonism (e.g. triceps)

• Others


3-D Biomechanical Models

• These models are difficult to build due to the increased

complexity of calculations and difficulties posed by

muscle geometry and indefiniteness.

• Additional problems introduced by indefinity; there are

fewer equations of equilibrium (balance) than unknowns

muscle forces.

• While 3-D models are difficult to construct and validate,

3-D components of lifting, especially lateral bending,

appear to significantly increase risk of injury.

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From Biomechanics to Task Evaluation

• Biomechanical analysis yields external moments at

selected joints

• Compare external moments with joint strength

(maximum internal moment)

– Typically use static data, since dynamic strength

data are limited

– Use appropriate strength data (i.e. same posture)

• Two Options:

– Compare moments with an individuals joint

strength

– Compare moments with population distributions to

obtain percentiles (more common)


Task Evaluation and Ergonomic Controls

• Demand (moments) < Capacity (strength)

• Are the demands excessive?

– Is the percentage capable too small?

– What is an appropriate percentage? [95% or 99%

capable commonly used]

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• Strategies to Improve the Task:

– Decrease Demand (D)

• Forces: masses, accelerations (increase or decrease,

depending on the specific task)

• Moment arms: distances, postures, work layout

– Increase Capacity (C)

• Design task to avoid loading of relatively weak joints

• Maximize joint strength

• Use only strong workers

Task Evaluation and Ergonomic Controls (cont.)

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