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Ergonomics > Midterm 2 > Flashcards

Midterm 2 Flashcards

1
Q

What are some general trends regarding the incidence of back injuries? Who is affected? How long do these injuries last?

A

Getting better through automation, 56% of back injuries are lower only. Working population aged 25-55 affected the most. Over 25% of injuries are 31+ days of lost time, 20% 3-5 days

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2
Q

What does the front part of the vertebra do?

A

Vertebral body is the load bearing structure.

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3
Q

What do the components on the posterior portion of the vertebra do?

A

Posterior elements are where the muscles attach via tendons. 7 cervical, 2 thoracic, 5 lumbar.

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4
Q

How are the posterior portions of the vertebra injured?

A

High rate of loading, pulling, pushing, repeated full motions

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5
Q

What are the factors that affect whether tendons and ligaments will be injured?

A

Direct trauma (lacerations, contusions, overuse). Rate of loading, amount of load, repetition. Ligaments - bone to bone, slow to heel, sprains, high % of collagen. Tendon - muscle to bone, overuse, higher % of collagen.

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6
Q

What does cartilage do?

A

Absorbs shock and distributes loads, prevents direct wear on bones by allowing relative movement of opposing joint surfaces with minimum friction and wear.

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7
Q

Where is cartilage found in the human body?

A

Fibrocartilage in discs, Hyaline in synovial joints and vertebral end-plates.

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8
Q

How are nutrients delivered to these tissues?

A

No blood vessels, through diffusion, slow recovery.

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9
Q

What are the two main parts of bone?

A

Outer(cortical) - compact bone provides strength and stiffness. Inner(trabecular) - provides large capacity for energy storage.

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10
Q

What is Wolf’s Law?

A

Bone remodels in response to mechanical load.

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11
Q

What kind of occupational injury concerns exist with bone tissue?

A

Fatigue fracture - osteoporosis in older workers, susceptibility to crush, military boot camps.

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12
Q

What are the primary parts of the intervertebral disc?

A

Nucleus Pulposus - resists compressive spinal loads, gelatinous mass in center, dries up with age. Annulus Firbrosus - elestic properties of disc, resists shear loads on the spine (along with facet joints).

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13
Q

What does the disc do?

A

Shock absorber, movable joint where motion occurs in spine, spacer allows room for nerve roots, nutrients diffuse through end plates and annulus, spinal motion acts as nutrition pump.

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14
Q

What is the vertebral end plate?

A

Connection between disc and vertebral body, made of hyaline cartilage.

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15
Q

Why is the vertebral end plate important?

A

It is porous and allows nutrient exchange with blood vessels in the vertebral body.

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16
Q

What type of health concerns exist for the intervertebral disc?

A

End plate fractures due to excessive compression loads, herniation associated with full end range of motion, cell death within the nucleus pulposus under loading, degeneration with age and load exposure.

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17
Q

What tissues can potentially be the source of back pain?

A

Disc, ligament, tendon, facet joint, muscle.

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18
Q

What is meant by “idiopathic low back pain?

A

85% of lower back pain you can’t see on x-rays.

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19
Q

Where is the Latissimus Dorsi and where does it connect?

A

Right and left side of the mid-back that connects to tissue called fascia, from the sacrum to the under arm.

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20
Q

Where is the Erector Spinae and where does it connect?

A

Fibers that run parallel to the spine and originate from the sacrum to the rib cage(Longissiums, illiocostallis, multifidus).

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21
Q

When do people use their Latissimus Dorsi muscle?

A

Pulling tasks.

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22
Q

When do people use their Erector Spinae muscle?

A

Lifting tasks.

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23
Q

In addition to back muscles, what other muscles support and help move the back and torso?

A

Posterior trunk muscles (deepest layer), Rectus abdominus, External/internal oblique, Transverse abdominus.

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24
Q

What is the difference between an agonist and an antagonist muscle?

A

Agonist(prime mover) initiates contraction necessary to move a limb through joins range of motion. Antagonist(reactionary) lengthens or stretches to allow agonist to complete action then contracts to return to original position.

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25
Q

For the spine which muscles are agonist muscles are which are antagonist muscles for flexion of the spine?

A

Agonist - rectus abdominus

Antogonist - erector spinae

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26
Q

For the spine which muscles are agonist muscles are which are antagonist muscles for holding a box?

A

Agonist - erector spinae

Antagonist - rectus abdominus

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27
Q

The amount of back muscle force needed in a particular lifting task depends on what?

A

Weight lifted and distance of reach (torque). Torque from the box equals the torque from the back.

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28
Q

What do the disc pressure studies show us?

A

Body position has a great effect on amount of load on the disc, angle of flexion and load both linearly correlate with disc pressure.

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29
Q

What is the relationship between spine compression force and low pain incidence rates?

A

Increased compression force leads to increased risk of injury. Incident rates jump when compression force is greater than 250 kg and again when greater than 650 kg.

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30
Q

How does the tolerance to spine compression change as a function of age?

A

The compression force resulting in disc-vertebrae failure goes down with age. Age less than 40 at 650 kg. Age greater than 60 at 375 kg.

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31
Q

Describe three loading scenarios by which tissues can become injured.

A
  1. When applied load is greater than tissue strength tissue failure occurs.
  2. When a single high intensity excessive load occurs tissue tolerance is exceeded.
  3. During repeated low level loading over time under a constant low applied load the tissue tolerance is reduced.
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32
Q

What are generic physical risk factors for musculoskeletal discomfort?

A

Awkward postures, excessive force, repetitive activity, lack of rest, environmental stressors.

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33
Q

Why is posture a risk factor for low back injury?

A

Muscle length changes with posture, pressure on facet joints increases, extreme forward bending puts stress on spinal ligaments.

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34
Q

Why are we concerned about spine twisting?

A

Twisting increase pressure on sliding spine joints and strains selected disc fibers.

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35
Q

What did the Lumbar Motion Monitor study show us about low back injury risk?

A

Lower back disorder risk distribution of repetitive, materials handling jobs have either high numbers of low-back strains or zero low-back strains and zero turn over.

36
Q

When are people exposed to whole body vibration?

A

When seated; vibration is linked to increased LBD risk.

37
Q

What are psychosocial factors?

A

Job enjoyment, variety lack, influences over work, social relations, supervisor and employee relations, concentration demands, responsibility stress.

38
Q

What can you say about the Boeing studies that define these risk factors?

A

45% measure accounted for a total variance: 12% psychosocial, 31% biomechanics.

39
Q

What are psychosocial factors important when considering the lost time associated with injuries?

A

Early return to work and communication and disabled employees.

40
Q

What is included in workplace parameters in the model?

A

Lifting, lowering, pushing, pulling, carrying, physical demand of tasks.

41
Q

What is included in individual parameters in the model?

A

Gender, age, injury history, motor control capability, muscle endurance, strength.

42
Q

What is included in work organization parameters in the model?

A

How long workers must perform tasks before doing something else.

43
Q

What is included in psychosocial parameters in the model?

A

Supervisor relations, job enjoyment.

44
Q

What can we say about seating and the pressure on the spine?

A

Arms dangling and leaned forward has the most pressure on discs and Standing has the least. Arms should be supported with back support.

45
Q

What happens with increased lumbar support of increasing back rest inclination angles?

A

Spine compression force decreases when you increase either seating parameter.

46
Q

What happens with arm rests and why?

A

Arm rests reduce disc pressure because it is less weight and moment if they are not dangling.

47
Q

What is the purpose of Balans chairs?

A

Accommodates for back pain and takes pressure off of discs. Transitions force to shins instead of spine.

48
Q

When you are providing seats to people who have historically stood, what are things you should consider?

A

Back support, leg room, leg length on the chair, chair height, arm rests, lumbar support, casters, breathable fabric, recline.

49
Q

When are incidents of the neck and shoulder pain more common?

A

Health care and computer work.

50
Q

What is the primary muscle and tendon often often implicated in rotator cuff shoulder pain?

A

Supraspinatus tendon and muscle.

51
Q

We sometimes talk about impingement of this muscle’s tendon. What bony part of the skeleton is responsible for this?

A

Acromion; when frequently raised inflames subdeltoid bursa.

52
Q

What is the relationship between shoulder abduction angle or shoulder flexion angle and shoulder fatigue?

A

Fatigue faster with greater angle due to increased moment.

53
Q

What is the relationship between reach distance and shoulder fatigue and why?

A

Greater reach distance has a faster fatigue rate because it increases the muscle length which increases the moment.

54
Q

What anatomical structures pass through the carpal tunnel in the wrist?

A

9 flexor tendons and the median nerve.

55
Q

Which nerves are responsible for sensation in the hand? Which pass through the carpal tunnel?

A

Radial, median and ulnar nerves provide sensation; the median nerve goes through the carpal tunnel.

56
Q

How do deviated postures affect hand strength and symptom experienced at work?

A 
Natural 0 degrees - 100%
Extension 45 degrees - 45% to 75%
Flexion 45 degrees - 60%
Radial 25 degrees - 80%
Ulnar 45 degrees - 75%
57
Q

How does grip span affect strength?

A

Grip is weaker the bigger or small the span is based off of the normal grip span and results in a bell curve.

58
Q

Define Carpal Tunnel Syndrome.

A

Compression of the median nerve.

59
Q

Define Tendonitis.

A

Inflammation of a tendon.

60
Q

Define Tenosynovitis.

A

Inflammation of the tendon sheath.

61
Q

Define DeQuervain’s disease.

A

Tenosynovitis of thumb.

62
Q

Define Lateral epicondylitis.

A

Inflammation of lateral elbow tissue due to forceful forearm rotation.

63
Q

How common is carpal tunnel syndrome?

A

7540 cases in 2012

64
Q

How much time is lost on average due to CTS?

A

30 days median, 8 days median for all lost time injuries, 3% MSDs.

65
Q

How is carpal tunnel syndrome assessed in an individual?

A

Symptoms include numbness, tingling, pain in wrists. Slowing of the nerve conduction velocity. Swelling of tendons initiates damage to median nerve.

66
Q

What did the monkey studies show us about carpal tunnel syndrome?

A

CTS will develop as a result of exposure to repetitive manual tasks that require moderately forceful exertions applied with a pinch grip.
Work related.
Reduction in sensory nerve conduction velocity and enlarged.

67
Q

What are the primary risk factors associated with upper-extremity cumulative trauma disorders?

A

High rates of manual repetition, high force required, postural stress, insufficient recovery time, sustained muscle use, vibration, cold temperatures.

68
Q

What is the relationship between neck posture and next symptoms?

A

Fatigues faster with greater head tilt.

Neck pain is related to head tilt.

69
Q

What are the factors that often influence next posture and use?

A

Work stations and equipment, distance away from the screen, screen height, working from documents, headsets versus phone.

70
Q

What is the difference between REBA and RULA?

A

REBA is whole body activities both static and dynamic.

RULA are sedentary tasks where upper body demands are high.

71
Q

What factors are included in the computation of the NIOSH lifting index?

A 
RWL = LC x HM x VM x DM x AM x FM x CM
LI = actual weight / RWL
72
Q

What are the key pieces of data necessary to analyze a potential vibration exposure problem?

A

Magnitude of acceleration, frequency of vibration, directionality, duration of exposure.

73
Q

How do you determine once you have those data whether you have a problem?

A

Low back pain, disturbance of central nervous system, white finger syndrome, increases heart rate, exposure leads to health impairment.
Reaching fatigue limit leads to performance being affected and reduced comfort boundaries.

74
Q

Why assess tibial shock?

A

The tibia is connected to feet, absorbing most of the vibrations in the feet of the fork lift workers.

75
Q

What do the tibial shock studies show us about lower extremity vibration exposure in distribution center forklift drivers?

A

Slowing down the forklift by 2 mph.
Dock plates need to be evaluated and replace regularly.
Adding a mat had no effect.
New shock absorbing truck had the largest effect.

76
Q

What are effective control approached for vibration?

A

Tool speed, mechanical devices, exposure time, adapt posture, reduce contact areas and training.

77
Q

How can you alter risk of injury by changing the work layout and what risk factors will likely be affected?

A

Create a design that permits two 90 degrees turns which reduces twisting in a full 180 degree turn.
Reach reduction, height adjustment, force reduction, postural relief and tool design.

78
Q

What are some mechanized approaches that can be used to facilitate lifting?

A

Spring-loaded bins, automatic scissor lifts, pallet jacks, articulating belt extension.

79
Q

What are some of the things one has to consider when looking into solutions that facilitate lifting?

A

Cost, impact to injuries and impact to productivity.

80
Q

How can you reduce reaching?

A

Lift and tilt bins and pick hooks.

81
Q

What are some of the different ways you adjust the height at which someone is working?

A

Platforms raise the work to elbow height.

Slot items by frequency.

82
Q

How can you reduce twisting in manual material handling work?

A

Redesign the layout and change the orientation of work.

83
Q

What are some ways to reduce push/pull forces?

A

Machine aiding systems, carts, electronic lifters for hospital patients.

84
Q

What are some ways to reduce hand forces required during assembly work?

A

Mechanize the task.

85
Q

How can we affect the wrist motion required in a manufacturing process?

A

Add fixtures.

86
Q

How can we affect the wrist motions found in piece-pick distribution operations?

A

Bend the tool not the wrist.

87
Q

What are the main principles that should guide the design or selection of hand tools used in a job?

A

Maintain straight wrists, avoid tissue compression, avoid repetitive finger action, design for safety, consider hand size range and left-handers, consider tool weight.

Ergonomics (3 decks)

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