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ISE 3624 > Industrial Ergonomics Unit 1 > Flashcards

Industrial Ergonomics Unit 1 Flashcards

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1
Q

What is Ergonomics?

A

Is the process of designing or evaluating products, tasks, environments, and systems to improve performance and/or reduce the risk of injury.

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2
Q

Acute or Chronic Musculoskeletal Disorders (MSDs)

A

Present in 12% of Population
32 million MS injuries per year
Nearly 2% of workers have work-related back problems each year
National systems markedly underestimate magnitudes

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3
Q

Cost of MSDs

A

The total cost of occupational injuries and illness in the US is >$150 Billion (nearly 3% of GDP)
More than AIDS, nearly equal to costs of cancer or heart disease
Injuries account for 85% of these costs, with MS injuries generating a large majority
Work-related MSDs account for ~1/3 of all workers compensation costs

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4
Q

Types of Physical Ergonomics Problems

A

Anthropometric problems
Musculoskeletal problems
Metabolic/Cardiovascular problems
Environmental problems

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5
Q

The Ergonomic Process

A
  1. Characterize existing or potential problems
  2. Perform job analysis
  3. Implement controls
  4. Evaluate the effectiveness of controls, and educate employees on ergonomics
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6
Q

Guiding Principle of Ergonomics

A

D (Demands) < C (Capacity or Capability)

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7
Q

6 Types of Interactions

A 
Human with Machine
Machine with Human
Human with Environment
Environment with Human
Machine with Environment
Environment with Machine
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8
Q

Stress Formula

A

Stress = Force/ Initial cross-sectional area

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9
Q

Strain Formula

A

Strain = Change in length/ Original length

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10
Q

Mechanical properties of bone

A
  1. Hooke’s law
  2. Young’s modulus (E)
  3. Yield stress
  4. Yield strain
  5. Ultimate stress
  6. Ultimate strain
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11
Q

Wolff’s Law

A

Bone (or other material) adapts to its mechanical environment: it will be added where needed and reabsorbed where not needed

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12
Q

Ligaments

A

Ligaments connect bone to bone

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13
Q

Tendons

A

Tendons connect muscles to bones

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14
Q

Structural differences between ligaments and tendons

A

Tendon fibers are parallel to one another due to the push and pull function of a tendon, while ligaments fibers are cross-sectional due to the variety of ways a ligament is pulled.

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15
Q

Cartilage

A

A smooth elastic tissue that covers the ends of long bones at joints to provide a low-friction for movement.

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16
Q

Fascia

A

A band or sheet of connective tissue, primarily collagen, beneath the skin that attaches, stabilizes, encloses, and separates muscles and other internal organs.

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17
Q

Viscoelasticity

A

Material response to force (or displacement) depends not only on force (or displacement), but also on time.

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18
Q

Creep

A

A change in strain for constant stress, and over time will reach a constant displacement

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19
Q

Load (stress) relaxation

A

A change in stress for constant strain, and over time will reach a constant force

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20
Q

Muscle Structure Units

A

(Largest) Muscle -> Fascicle -> muscle fiber -> myofilament (Smallest)

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21
Q

Myofilaments

A

Thin (actin) filaments

Thick (myosin) filaments

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22
Q

How does a muscle contract

A

Muscles contract not because of shortening of individual myofilaments, but because they slide

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23
Q

Types of muscle contractions

A

Isometric- constant length (or joint angle)
Concentric- muscle shortening
Eccentric- muscle lengthening,&raquo_space;> external load (plyometric)
Isokinetic- constant velocity (or joint angular velocity)
Isotonic- constant force (or moment)

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24
Q

Muscle groupings

A

Co-contraction- two or more muscles contracting at the same time
Agonist- contributes to the desired effort
Antagonist- opposes desired effort

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25
Force-length Relationship
The amount of force a muscle can produce depends upon its length. Muscle force also depends upon passive tension
26
Force-Velocity Relationship
The amount of force a muscle can produce depends upon its velocity (rate of change of length)
27
Force-Activation Relationship
The amount of force a muscle produces depends upon its activation level (0-100%)
28
The Motor Unit
A single nerve and all of the muscle fibers it innervates
29
3 Types of Muscle Fibers
Slow (Type I) and fast (Type IIaand Type IIb ) fibers
30
Muscle Spindles
Are specialized muscle fibers that provide CNS feedback on muscle strain (length) and strain rate (velocity)
31
Golgi Tendon Organs
Golgi tendon organs provide CNS feedback on muscle force. Oriented in series with muscle, act as a force gauge
32
WMSDs
Work tasks and environment contribute significantly to the condition, and likely make it worse or persist longer Involve injury to soft tissues of the body and joints They develop gradually over time The injury event, or the exposure leading to the event, involves bodily action, overexertion, or repetitive motion. WMSDs do not include sudden injuries such as those from slips, trips, and falls, or motor vehicle accidents
33
What is a risk factor?
A risk factor is an individual characteristic or exposure associated with an increased risk of a disease or injury.
34
Individual risk factors for WMSDs
``` Age Sex Obesity (anthropometry) Systemic diseases (e.g. diabetes) Acute trauma Congenital conditions ```
35
Task-related risk factors for WMSDs
``` High force exertions Highly repetitive work or static work Awkward or extreme postures Vibration Contact mechanical stress Environmental stress ```
36
Psychosocial risk factors for WMSDs
``` Psychological factors (individual-level) and social factors (organization-level) that influence the mental state of the individual Examples: mental stress, supervisory control, autonomy, job security, interaction with coworkers, anxiety, etc. ```
37
Tendon Disorders
Tendonitis: Inflammation of the tendon Tenosynovitis: Inflammation of tendon sheath
38
Hierarchy of Controls
Elimination, Substitution, Engineering Controls, Administrative Controls, PPE
39
Characterize existing or potential problems
Quantify injuries or performances issues | Identify tasks that may have risk factors
40
Evaluate the effectiveness of controls, and educate employees on ergonomics
Provide employees with a basic awareness of ergonomics principles. Involve workers in the process. They have the most knowledge about their jobs. They may already know how to improve them.
41
Awkward or Extreme Posture
Awkward posture- requires excessive effort against gravity or other issues Extreme posture- at or near a joint’s limits of motion
42
Awkward or Extreme Posture: Job Analysis
Determine frequency, duration, and/or magnitude of awk/extreme postures
43
ErgonomicsHigh Force Exertions: Job Analysis
Determine frequency, duration, and/or magnitude of forceful exertions
44
Contact Mechanical Stress: Job Analysis
Determine frequency, duration, and/or magnitude of contact force
45
Anthropometry
Is the study of the physical dimensions of the human body
46
Two types of anthropometric data
1. Static anthropometry: Physical dimensions of the body | 2. Functional or dynamic anthropometry: physical dimensions for completing particular activities or tasks
47
Units of mass conversions (lbs)
1 kg = 2.2 pounds | 1 slug = 32.2 pounds
48
Center of mass
COM is the point at which all the mass of a body can be concentrated so that it results in external forces and moments equivalent to the actual distributed body
49
General Design Strategies to account for anthropometric variance
Design for average Design for extremes (maximum or minimum) Design for Adjustability
50
Limitations of using Anthrodata to Design
Population-based data can have selection bias Averages and proportions don't represent individuals; people are not proportional Functional data may vary with clothing, protective equipment, etc. Even if guidelines, standards, etc. are followed, the workstation may not be completely functional, useable, or comfortable!
51
Why evaluate ROM and strength?
Identify high-risk work tasks Identify high-risk workers –Workers with limited capacities may be at elevated risk for WMSD, etc. Assess "Return to Work" status -Determine physical capacity after an injury to evaluate how much recovery has occurred. More broadly, help improve understanding of how individual risk factors affect worker capacity
52
Two types of ROM measurement
Active ROM: muscle force used to reach ROM limits, so also dependent upon muscle contraction Passive ROM: external force used to reach ROM limits; more dependent upon passive elasticity of MLTs Active ROM < Passive ROM
53
Describing Joint Motions
Anatomical Position and Anatomical Planes of Motion
54
Anatomical Terms Related to Movement
Flexion and extension movements occur in the sagittal plane Abduction and adduction movements occur in the frontal plane Rotation movements occur in the transverse plane
55
Methods to measure joint ROM
goniometer: measures the joint angle Inclinometer: measures the angles of slope, elevation, or depression of joint
56
Individual Factors Affecting ROM
Age Sex Training Joint or muscle pathology, genetics
57
Muscle Strength
Defined as the maximum force/moment a group of muscles can develop under prescribed conditions
58
Types of Muscle Strength Measurement
Isometric (static): no motion | Dynamic: strength test allowing motion
59
Factors affecting strength: Posture
Force - length relationship Changes in tendon moment arm with respect to the joint Changes in weight moment arm Two-joint muscles(muscle length depends upon two joint angles)
60
Factors affecting strength: Sex
Women are generally weaker than men by an average of about 35% to 85% The magnitude of sex difference is task-dependent When corrected for muscle x-section and lean body mass, values are nearly equal!
61
Factors affecting strength: Age
Muscle strength normally greatest in the late twenties to early thirties, and typically starts to decline in the 40s.

ISE 3624 (3 decks)

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