Fall 2006 SAFE4000; NSC Text Chap 4 1

NSC Text

Chapter 4 -

Anthropometry & Workplace

Stressors

Fall 2006 SAFE4000; NSC Text Chap 4 2

Anthropometry

Measuring the human Height, breadth, depth &

distance straight line measurements Curvatures & circumferences

Fall 2006 SAFE4000; NSC Text Chap 4 3

Anthropometry

“Average worker” No worker is average in every

physical dimension Workers in separate workplaces

are likely different

Fall 2006 SAFE4000; NSC Text Chap 4 4

Anthropometry

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

Fall 2006 SAFE4000; NSC Text Chap 4 5

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

Fall 2006 SAFE4000; NSC Text Chap 4 6

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

Fall 2006 SAFE4000; NSC Text Chap 4 7

Anthropometry - Workstations

Should accommodate varying sizes & reaches

Adjustability is key

Fall 2006 SAFE4000; NSC Text Chap 4 8

Stressors

Stress results when outside forces exceed person’s tolerance

Results in bodily/mental tension

Fall 2006 SAFE4000; NSC Text Chap 4 9

Stressors

Sources of stress–Physiological

–Biomechanical

–Psychological

Fall 2006 SAFE4000; NSC Text Chap 4 10

Fatigue

No precise definition Fatigue refers to

– General feelings of tiredness

– Reduction in work output

– Physiological conditions resulting from continued work activity

Fall 2006 SAFE4000; NSC Text Chap 4 11

Manifestations of Fatigue

Muscular soreness Aches Sleepiness Mental confusion Muscular tension General weariness

Fall 2006 SAFE4000; NSC Text Chap 4 12

Fatigue

Fatigue can result from physical or mental stressors

Mental Fatigue – Tiredness that occurs from

mental rather than physical work

Fall 2006 SAFE4000; NSC Text Chap 4 13

Physiological Stressors

Kinetic stress results when body is subjected to rapid accelerations

One example is vehicular maneuvers

Fall 2006 SAFE4000; NSC Text Chap 4 14

Rapid Accelerations

Blood flow changes & may cause:– Loss peripheral vision

– Illusions of motion

– Total loss of vision

– Loss of fine motor control

– Unconsciousness

Fall 2006 SAFE4000; NSC Text Chap 4 15

Vibrations & acoustic noise may be considered together because they are both mechanical oscillations

Fall 2006 SAFE4000; NSC Text Chap 4 16

Both may interfere with other sensory functions & disrupt motor coordination & actual feedback

Fall 2006 SAFE4000; NSC Text Chap 4 17

Vibrations & Noise

Persistent noise induces anxiety & irritation

Severe V&N may interfere with internal organs & CNS– Discomfort

– Disability

– Death

Fall 2006 SAFE4000; NSC Text Chap 4 18

Other Types Of Physiological Stressors

Thermal - heat stroke Atmospheric - decomp sick,

anoxia Chemical - inhalation/ingestion Radiation - symptoms range

from mild to death

Fall 2006 SAFE4000; NSC Text Chap 4 19

Other Types Of Physiological Stressors

Physical work overload - extreme muscular exertion

affects coordination & strength can lead to muscle spasm or

collapse

Fall 2006 SAFE4000; NSC Text Chap 4 20

Other Types Of Physiological Stressors

Glare– annoyance,

– discomfort

– visual problem Sleep deprivation - effects

performance

Fall 2006 SAFE4000; NSC Text Chap 4 21

Sleep Deprivation

Can Adversely affect decision making process, may result in:– weariness

– decreased strength

– irritation

– poor vision

– hallucinations

Fall 2006 SAFE4000; NSC Text Chap 4 22

Psychological Stressors

Psychological Stressors may cause mental stress

Because tension may result in physiological problems...

may be unable to differentiate between physiological & psychological stressors

Fall 2006 SAFE4000; NSC Text Chap 4 23

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

Fall 2006 SAFE4000; NSC Text Chap 4 24

Psychological Stressors

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

Fall 2006 SAFE4000; NSC Text Chap 4 25

Monotony

Monotony results from inactivity, boredom, repetitive tasks

Mind dulling effects of monotony can seriously degrade performance

Fall 2006 SAFE4000; NSC Text Chap 4 26

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

Fall 2006 SAFE4000; NSC Text Chap 4 27

Excessive Task Speed/Load

…requirements can cause psychological & physical stress

This stress is associated with concern that task be completed successfully within time allotted

Fall 2006 SAFE4000; NSC Text Chap 4 28

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

Fall 2006 SAFE4000; NSC Text Chap 4 29

Circadian Rhythm

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

Fall 2006 SAFE4000; NSC Text Chap 4 30

Stress may also be the result of worker’s “life situation” external to the work environment

Fall 2006 SAFE4000; NSC Text Chap 4 31

NSC Text

End Of Chapter 4