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• Chapter 4 -
• Anthropometry Workplace
• Stressors

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Anthropometry

• Measuring the human
• Height, breadth, depth distance
• straight line measurements
• Curvatures circumferences

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Anthropometry

• Average worker
• No worker is average in every physical dimension
• Workers in separate workplaces are likely
  different

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Anthropometry

• Workplaces designed to accommodate 90 of
  population, leave out who?

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Anthropometry

• Much of the available data (tables 4-1 4-2) is
  adapted from US military
• Such data can help in designing workstations
  job tasks

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Military Anthropometric Data

• Biased toward younger workers
• Close correlation to civilians except for
  hgt/wgt of females
• limited data in figs 4-1 4-2

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Anthropometry - Workstations

• Should accommodate varying sizes reaches
• Adjustability is key

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Stressors

• Stress results when outside forces exceed
  persons tolerance
• Results in bodily/mental tension

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Stressors

• Sources of stress
• Physiological
• Biomechanical
• Psychological

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Fatigue

• No precise definition
• Fatigue refers to
• General feelings of tiredness
• Reduction in work output
• Physiological conditions resulting from continued
  work activity

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Manifestations of Fatigue

• Muscular soreness
• Aches
• Sleepiness
• Mental confusion
• Muscular tension
• General weariness

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Fatigue

• Fatigue can result from physical or mental
  stressors
• Mental Fatigue
• Tiredness that occurs from mental rather than
  physical work

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Physiological Stressors

• Kinetic stress results when body is subjected to
  rapid accelerations
• One example is vehicular maneuvers

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Rapid Accelerations

• Blood flow changes may cause
• Loss peripheral vision
• Illusions of motion
• Total loss of vision
• Loss of fine motor control
• Unconsciousness

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Vibrations acoustic noise may be considered
together because they are both mechanical
oscillations
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Both may interfere with other sensory functions
disrupt motor coordination actual feedback
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Vibrations Noise

• Persistent noise induces anxiety irritation
• Severe VN may interfere with internal organs
  CNS
• Discomfort
• Disability
• Death

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Other Types Of Physiological Stressors

• Thermal - heat stroke
• Atmospheric - decomp sick, anoxia
• Chemical - inhalation/ingestion
• Radiation - symptoms range from mild to death

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Other Types Of Physiological Stressors

• Physical work overload - extreme muscular
  exertion affects coordination strength can lead
  to muscle spasm or collapse

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Other Types Of Physiological Stressors

• Glare
• annoyance,
• discomfort
• visual problem
• Sleep deprivation - effects performance

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Sleep Deprivation

• Can Adversely affect decision making process, may
  result in
• weariness
• decreased strength
• irritation
• poor vision
• hallucinations

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Psychological Stressors

• Psychological Stressors may cause mental stress
• Because tension may result in physiological
  problems...
• may be unable to differentiate between
  physiological psychological stressors

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Psychological Stressors

• Ergonomists do not attempt to eliminate all
  sources of stress
• Not all stress is disruptive
• Limited amounts of stress serve to motivate
  workers

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Psychological Stressors

• Too much concern or anxiety may cause operator to
  spend too much time focusing on selected displays
  neglect other duties

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Monotony

• Monotony results from inactivity, boredom,
  repetitive tasks
• Mind dulling effects of monotony can seriously
  degrade performance

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Monotony

• Uneventful vigilance tasks are examples tasks
  that produce stress via monotony
• Closely aligned with monotony is sensory
  deprivation
• Occurs when person is isolated from any
  perceptual input

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Excessive Task Speed/Load

• requirements can cause psychological physical
  stress
• This stress is associated with concern that task
  be completed successfully within time allotted

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Circadian Rhythm

• 24 hr cycle of night day
• Basis for our regulation of eating sleeping,
  working, socializing
• Disruptions can serve as both psychological
  physiological stressors

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Circadian Rhythm

• Disruptions (changes in work shift) can result in
  autonomic nervous system changes neuro
  endocrine changes that are stressful

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Stress may also be the result of workers life
situation external to the work environment
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• End Of Chapter 4