Introduction to Ergonomics

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Introduction to Ergonomics
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Engineering

• Definitions
• Process

Problem symptom or need
Problem Definition, Statement of Desired Outcome
Analysis (Experimentation?)
Synthesis of Alternative Solutions
Decision (Selection)
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Process Example

• What are the design considerations for a
  prosthetic Leg?

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Ergonomics - Introduction

• Derived from the Greek nomos natural laws,
  ergon work
• Definition discipline that uses knowledge of
  human abilities to design systems, jobs, tools,
  and products for the safe and efficient execution
  of work.
• Ergonomic Objective
• Worker Capacity lt Job Demands

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Ergonomics - Introduction

• Worker Capacity lt Job Demands
• Methods
• Workplace and Equipment Design
• Tool Design
• Design of Work Methods
• Matching Capabilities and Limitations of Worker

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Ergonomics Introduction

• Why Important?
• Specialization / Automation
• Diversity of Workforce / Labor Laws
• Gender
• Aging Population
• Injured, Disabled workers
• Increase Productivity / Competitive Advantage
• Prevent Injury / Reduce workers Comp Costs
• Societal Quality of Life

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Ergonomics and Physiology

• Relevant Subject Areas
• Muscular
• Nervous
• Circulatory
• Digestive
• Psychosocial
• Cognitive
• Sensory

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Ergonomics and Physics

• Force
• Regularly exerted ON the body and BY the body
• Fma
• Acts in a linear direction
• Muscles generate force

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Ergonomics and Physics

• Torque
• MFD
• Acts as a moment about a fixed point
• Muscles in conjunction with tendons, joins, and
  ligaments generate torque.

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Ergonomics and Physics

• Pressure
• Imparted BY the body and ON the body
• PF/A
• Examples

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Occupational Injury

• Difference between Ergonomics and Safety?
• Cumulative Trauma Disorders (CTD)
• Definition Bodily injury associated with
  repeated biomechanical stress over time.

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Occupational Injury

• Risk Factors for Cumulative Trauma Disorders

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Cumulative Trauma Disorders

• Bursitis
• Tendonitis
• Tenosynovitis
• Tendon injury involving the synovial sheath,
  caused when excessive amounts of synovial fluid
  are created due to extreme repetition. Sheath
  becomes swollen or painful.

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Cumulative Trauma Disorders

• De Quervains Disease
• Tenosynovitis in the tendons at the base of the
  thumb.
• Finkelstein Test

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Cumulative Trauma Disorders

• Trigger Finger (Flexor Tendonitis)
• Tendon swelling interferes with the normal
  movement of the tendons through the synovial
  sheath and can cause the finger to click, catch,
  or lock in position

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Cumulative Trauma Disorders

• Carpal Tunnel Syndrome
• Impaired nervous function in the first three
  digits manifested as numbness, tingling, pain,
  and loss of dexterity.
• Median nerve inside the wrist becomes compressed
  due to inflammation or thickening of adjacent
  tendon sheaths. Inflammation may be caused by
  overexertion or repeated unsafe wrist
  orientations.

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Tool Design Guidelines

• Improper Tool Design May Cause
• Increased grip forces (CTD)
• Unwanted postures (CTD)
• Acute Trauma (Burns, cuts, lacerations,
  abrasions, fractures, strains, sprains,
  dislocations, etc.)
• Reduced Productivity

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Tool Design Guidelines

• Situations to avoid
• Sustained Ulnar/Radial Wrist deviation
• Excessive or repeated flexion/extension of hand
  and wrist
• Excessive force
• Impact shocks
• Tissue compression from sharp edges or
  misdirected forces
• Ischemia obstruction of blood flow to the
  tissues and eventual numbness or tingling

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Tool Design Guidelines

• Types of Grip
• Power
• Precision
• Design for Population
• Gender
• Left/Right Handedness

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Tool Design Guidelines

• Handle
• Diameter
• Length
• Shape
• Surface (material)
• Angulation
• Grip Span
• Weight

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Examples

• Pliers
• Knives
• Scissors

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Engineering Design Constraints

• Example The Vibration Dilemma

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The Future

• Workplace and Equipment Design