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Psy 552 Ergonomics

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Psy 552 Ergonomics & Biomechanics Lecture 17 Work classification methods The need to address productivity, comfort and safety dictate the need evaluate work methods. – PowerPoint PPT presentation

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Title: Psy 552 Ergonomics


1
Psy 552 Ergonomics Biomechanics
  • Lecture 17

2
Work classification methods
  • The need to address productivity, comfort and
    safety dictate the need evaluate work methods.
  • In the quest to find the optimal method, early
    methods focused on productivity.
  • These work analysis methods have significant
    drawbacks that limit their use in ergonomics and
    biomechanics.

3
Historic names
  • Frederick Taylor father of timemotion studies.
  • Used time analysis of work to enhance
    productivity.
  • Devised the four principles of
  • scientific management

4
4 Principles
  • Study work methods specifically.
  • Select the best workers for the task and train
    them.
  • Develop cooperation between employees and
    managers.
  • Divide work according to ability, between workers
    and managers depending upon who was best suited
    to perform it.

5
Frank and Lillian Gilbreth
  • Studied work methods
  • Capitalized on motion studies using illuminated
    markers.
  • Categorized motions in to elemental motions
    that now serve as the basis for contemporary time
    and motion studies.

6
Method-Time Measurement (MTM)
  • MTM is a time estimation based upon elemental
    movements

7
MTM (cont)
  • Focuses on how
  • ...
  • Uses TMUs

8
Time motion ergonomics
  • These early studies created a foundation for
    ergonomic evaluations.
  • TM studies do not generalize to ergonomics
    biomechanics because they

9
Contemporary classification methods
  • Modern systems fall into two categories
  • Passive
  • Active

10
Passive surveillance
  • Involves reviewing and analyzing pre-existing
    records such as

11
The passive process
  • Must be contrasted with results of other
    assessment techniques including

12
The passive process (cont)
  • Works best when records are computerized.
  • Should be conducted monthly if not quarterly.
  • Should contain requisite information

13
Indices
  • Incident rate
  • IR ( of illnesses x 200,000)/hours worked
  • Point prevalence
  • PR ( new old case at a given time)/number
    of workers at the same time
  • Severity index
  • SI (Total lost work days due to the
    disorder(s))/(Total number of workers or hours
    worked in a period)

14
Passive advantages
  • Low cost
  • Makes use of available data
  • Historical perspective
  • Can be used to compare departments
  • Can be used to evaluate ergonomic interventions

15
Passive disadvantages
  • There are few accepted signs for WMSD.
  • The true causes of WMSD are not well known.
  • Putative factors are present in every job.
  • These factors dont discriminate or differentiate
    jobs with and without histories of WMSD.
  • Underreporting

16
Passive disadvantages (cont)
  • Inconsistent record collection
  • WMSD occur over time and might not be reflected
    in records.
  • Unknown reporting thresholds
  • Records often fail to record the specific task
    being performed.

17
Active surveillance
  • There are two types
  • Self-report
  • Audits
  • Advantages

18
Active surveillance (cont)
  • Success depends on
  • Short response times
  • Adequate response rates
  • Trained personnel
  • Employee memory
  • Tolerance of false positives

19
Active self-report tool features
  • 1.
  • 2.
  • 3.
  • 4.
  • 5.
  • 6.
  • 7.
  • 8.
  • 9.

20
Demographic medical work history
21
Analyzing WMSD data
WMSD WMSD WMSD
Yes No Total
Risk Factor Present Yes 10 30 40
Risk Factor Present No 4 76 80
Total 14 106 120
22
Analyzing WMSD data (cont)
  • WMSD incident rates gt 1 per 200,000 should be
    investigated further.
  • In Washington State between 1988 and 1991 the
    WMSD incident rate was .82 per 200,000 work
    hours.
  • Prioritize
  • Jobs with the highest incident rates.
  • Jobs with the most effected people.
  • Jobs where large changes have taken place.

23
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24
Active surveillance Risk factors
  • Used by trained ergonomist
  • Provide data based on educated observations
  • Do not require preexisting symptoms
  • Can be used to evaluate work or equipment
    changes.
  • Highly correlated with discomfort surveys.

25
Risk factors (cont)
  • Posture targeting
  • Ovac Working Posture Analysis System
  • EMG

26
Risk factor surveillance Disadvantages
  • They are more descriptive than evaluative.
  • A risk factor absent an injury requires evaluator
    judgment.
  • There are often few comparisons.

27
When conducting evaluations
  • Cleary state your objectives.
  • Understand sponsors desires.
  • Understand that you will not be universally
    accepted.
  • Select methods using an iterative process to
    promote validity.
  • Seek most recent scientific literature.
  • Seek advice of experienced colleagues.
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