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?

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1 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? 1

2 Steps to identify and preempt 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 What is Ergonomics? Wisdom 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 wellbeing 2

3 What is Ergonomics? Wisdom (cont.) 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? -Life-Cycle of Products- 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 3

4 What is Ergonomics? - Life-Cycle of Products- (cont.) 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 Occupational Biomechanics? 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) 4

5 Biomechanics What is it? The mechanical bases of biological systems. The application of mechanical laws to living structures. Biomechanical Modeling Methods Kinesiology Methods Anthropometric Methods Mechanical Work Capacity Evaluation Methods Bioinstrumentation Methods Classifying and Evaluating Work OCCUPATIONAL ERGONOMICS & BIOMECHANICS Worker Selection Criteria & Training Hand Tool Design Guidelines Workplace & Machine Guidelines Seating Design Guidelines Material Handling Limits [Chaffin et al, 1999] Improved Performance & Reduced Risk of Mechanical Trauma 5

6 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. 6

7 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. 7

8 Biomechanics: Does it exist in more than one field? Exercise and sport biomechanics Orthopedic biomechanics Occupational biomechanics Biomechanics of other biological systems Biomechanics: Does it exist in more than one field? Exercise and sport biomechanics improving athletic performance, reduction of athletic injuries 8

9 Biomechanics: Does it exist in more than one field? Orthopedic biomechanics artificial limbs, joints, and orthoses to improve functional movement capacity study of natural and artificial biological tissues Biomechanics: Does it exist in more than one field? Occupational Biomechanics Ergonomics and Human Factors reduction of workplace injuries 9

10 Biomechanics: Does it exist in more than one field? 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. 10

11 (Bio)mechanics Deformable Statics Dynamics Fluids Solids Kinematics Kinetics Stress Strain Linear Angular Divisions of Mechanics 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? 11

12 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. 12

13 2-D Model of the Elbow: Unknown Elbow force and moment 17.0 cm 10 N 35.0 cm 180 N From Chaffin, DB and Andersson, GBJ (1991) Occupational Biomechanics. 2-D Model of the Elbow: From Chaffin, DB and Andersson, GBJ (1991) Occupational Biomechanics. Fig

14 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. 14

15 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] 15

16 Task Evaluation and Ergonomic Controls (cont.) 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 References Chaffin et al., Occupational Biomechanics,

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