My Class

1

IE 552 Mechanics of Musculoskeletal System Dr.
Andris Freivalds Class 35
2
Gross Posture Analysis OWAS

• Owaco Working Posture Analysis System (OWAS,
  Karhu, 1977)
• Developed at the Finnish Institute of
  Occupational Health in 1970s
• For use in steel industry
• Evaluation of posture at regular intervals
• Four categories back, upper limbs, lower limbs,
  force (lt10, lt20, gt20 kg)

3
2151 bent back, both arms below shoulders,
kneeling, lt10 kg load
4
Gross Posture Analysis OWAS

• Next produce frequency distributions of OWAS
  postures
• Rate into four level of action categories
• Test-retest correlations high, r 0.97
• Quick but simple means of categorizing gross
  postures

5
Gross Posture Analysis - RULA

• Rapid upper limb assessment (RULA)
• Developed at the Univ. of Nottingham
• (McActamney and Corlett, 1993)
• Upper limb postures from Group A (for left or
  right side) are combined based on Table A to
  yield an upper limb score
• Trunk/leg postures from Group B are combined
  based on Table B to yield a trunk score

6
RULA Group A
7
RULA Table A
8
RULA Group B
9
RULA Table B
10
RULA Grand Score Table
11
RULA

• These scores are adjusted upwards
• 1 if mainly static posture (gt1 min) or
  . repeated gt 4/min
• 1 if 2-10 kg intermittent loads
• 2 if 2-10 kg static or repeated loads
• 3 if gt10 kg static or repeated loads
• Both scores combined into grand score
• Determines risk or action level

12
RULA

• If RULA grand score
• 1 or 2 acceptable conditions
• 3 or 4 change may be needed
• 5 or 6 change required soon
• 7 or 8 change required immediately
• Good correlation with discomfort
• Probably best for postural evaluations
• Example t-shirt turning, 12/min

13
(No Transcript)
14
RULA A 4 1 (Freq gt 4/min)
15
1 due to static posture
16
Grand score 4, Borderline risk
17
Quantitative Upper Limb WRMSD Risk Assessment
Strain Index 1

• Strain Index (SI, Moore and Garg, 1995)
• Rate 6 task variables (Table 1)
• intensity of exertion
• duration of exertion
• efforts per minute
• wrist posture
• speed of work
• duration of task

18
Strain Index Rating Criteria Table 1
19
Strain Index - 2

• Convert SI ratings to multipliers (Table 2)
• Multiply for final SI score
• Scores gt 5 considered hazardous
• Good validation
• identified 24/25 risky/non-risky jobs
• sensitivity 0.86
• specificity 0.79

20
Strain Index Multipliers - Table 2
21
Strain Index - 2

• Example using Strain Index
• Consider task with
• 20 MVC exertions
• over 60 of a cycle
• with 12 efforts per minute
• with 18 ulnar deviations
• at 95 of normal pace
• for a full 8-hr shift

22
(No Transcript)
23
Quantitative Upper Limb WRMSD Risk Assessment

• The example job is hazardous (13.5gt5)
• Overall, SI improvement over RULA
• Considers more than basic postures
• Considers upper extremities
• Considers effort, intensity, pace
• Greater quantitative detail
• Next step ? data driven risk models

24
Data Driven Upper Limb WRMSD Risk Assessment
PSU CTD Risk Index

• Developed at Penn State University
• From 13 years of Center for CTD work
• Wrist postures fed directly to model
• From touch glove system (using force sensitive
  resistors and Data Glove)
• Industrial WRSMD data tunes model
• Final score - predicted incidence rate
• Details - Seth, Weston, Freivalds (1999)

25
(No Transcript)
26
PSU CTD Risk Index - 2

• Validation on 24 jobs with 288 workers
• Regression of predicted vs. actual IR
• Significant (p lt 0.001) correlation, r2 0.52
• By 5th trial, analysis time down to 12 min.
• Test/retest reliability was up to r20.99
• 2nd validation on 91 meatpackers, r2 0.75

27
(No Transcript)
28
PSU CTD Risk Index - 3

• Also a paper and pencil version
• Quicker, simpler to use for industry
• Validated with PC version
• On 12 sewing jobs
• Significant (p lt 0.001) correlation of scores
  with r2 0.66
• Action level 1.0 (similar to NIOSH Lifting)

29
(No Transcript)
30
PSU CTD Risk Index P/P 1
31
PSU CTD Risk Index P/P 2