My Class

1

IE 553 Engineering of Human Work Dr. Andris
Freivalds Class 6
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IE 553 Engineering of Human Work Dr. Andris
Freivalds Class 6
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Mechanical Work Capacity Evaluation (Ch. 4)

• For any measurement, concerned for
• Standardization follow same procedures
• Accuracy (validity) closeness to truth
• Repeatability closeness of grouping
• Test-retest r
• Coefficient of variation (CV) s/µ
• Ease of use (industry vs. lab)
• Flexibility, interference on job
• Cost (industry vs. lab)

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Defining Joint Motion 1) For job requirements 2)
Input to biomech models
Standard Anatomical Position

• Planes
• Sagittal
• Frontal
• Transverse

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Defining Joint Motion
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Goniometers - 1

• Goniometer (protractor)
• Elgon (potentiometer)
• Flexometer (gravity sensing)
• Spatial imaging
• Photogrammetry (cameras)
• Computer collected (Vicon)

http//www.vicon.com/
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Goniometers -2
PennyGiles/Biometrics
Lumbar Motion Monitor
http//www.nexgenergo.com/ergonomics/biosensors.ht
ml
http//www.nexgenergo.com/ergonomics/lumbarmm.html
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Range of Motion

• Age 0-10 base, 10-16 10?, gt16 constant
• Gender Fem gt Males (by 10)
• Obesity ? ROM, ? bulk, ? activity
• Exercise ? flexibility
• Two-joint muscle effect
• Due to length-tension relationship
• 47? shoulder flex with elbow flex
• Passive vs volitional ROM

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Muscle Strength

• Need for strength evaluation
• Safe, healthy working conditions
• Inputs to biomechanical models
• MVC (max voluntary contraction)
• Must be lt bone/tissue yield strength
• Typically 30
• Must gt job strength requirements (JSR)
• Otherwise injury

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Static (Isometric) Strength
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Static Strength Testing Guidelines(Caldwell
regimen - AIHA (1974))

• Instructions Increase slowly and hold
• Duration of 4-6 seconds
• Record peak and 3-sec average
• Adequate rest, 2 min between trials
• 3 repetitions (need µ, s)
• Avoid coercion, environmental distractions
• Standardize test procedures
• Record subject attributes
• Safe (lt1/1,000), reliable (r gt 0.89), quick
  (10min)

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Effect of Posture on Strength
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Basis for ROM Variation
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Extensive Population Data(UM PEST, 1978)
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Dynamic vs. Static Strength

• Static underpredicts max lifting capability by
  50
• Due to angled pull
• Static overpredicts max lifting capability by
  10-20
• Due to inertial effects
• Dynamic better?
• R 0.9 with max lift (Kamon,1981)
• But much more variable
• Plus force-velocity effect
• Need isokinetic control

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Dynamic (Isokinetic) Strength
Cybex
MiniGym
KinCom