Upper Extremity Analysis Tools

• Risk Factors RULA considers

  • Number of movements/repetitions
  • Duration without a break
  • Force
  • Static muscle work
• Recording Working Postures on RULA

  • Body Divided into 2 Groups: Shoulder/Arm/Wrist & Neck/Trunk/Legs
  • Scoring System Based on OWAS System: "1" given for minimal risk, increasing values given to more extreme postures
• Strengths of RULA

  • Great for quick survey of a workplace
  • Allows for prioritization of tasks needing a "deeper dive" analysis
  • Gives a general score for whole body, with separate scores for the 2 groups
• Limitations of RULA

  • Limited assessment of force/repetition & hand demands
  • Doesn't provide evidence for acceptability of a task
• RULA Score Development

  • Developed "Muscle Use & Force" Scoring System
  • Developed grand score system by combining effects for groups A & B (score of 1-7), & then is further binned into 4 "Action Levels"
  • Posture ranges developed based on literature
  • 2 ergonomists & 1 physiotherapist looked at each possible combination of scores (assigned score of 1-9), & resolved inconsistencies & consolidated their results
• Validity of RULA

  • 16 operators, 2 postures, 8 tasks
  • Reported Body Part Discomfort (BPD)
  • Individual Segments: significant relationship between RULA score & BPD for neck & lower arm, but not for other segments
  • Group Segments: good relationship when combined across groups
• Reliability of RULA

  • 120 physiotherapists, industrial engineers, safety & production engineers
  • Videotaped records
  • Included Tasks = VDT, packing, sewing, brick sorting
  • "High consistency among subjects" except at borders of ranges
  • Pretty reliable
• Identified Task Variables for Strain Index

  • Intensity of Exertion
  • Duration of Exertion (% of cycle)
  • Frequency (efforts per minute)
  • Hand/Wrist Posture
  • Speed of Work
  • Duration per Day
• Strain Index is based on the integration of physiology, biomechanics, & epidemiology
• Evaluation of Strain Index

  • 2 authors rated 25 tasks
  • Determined morbidity/incidence of injury for each job
  • Results : rated all 13 "safe" jobs as safe, 11 of 12 "hazardous" jobs as hazardous
• Using Strain Index

  • Intensity of Efforts: Borg scale, % muscle strength, or perceived effort
  • Duration of Exertion: ((effort time)(# efforts in a cycle)/(cycle time))
  • Efforts per Minute: (# efforts in a cycle)/(cycle time)
  • Hand/Wrist Posture: pick worst posture when circling multiplier
  • Speed of Work: perceived speed, compared to MTM
  • Duration per Day: (cycle time) x (# of cycles per day)
  • Multiply the 6 numbers to get Strain Index
• Values for Strain Index

  • <3 is probably safe
  • >7 is probably hazardous
• Intensity has the largest effect on Strain Index result
• Original ACGIH-TLV For Hand Activity evaluates risk factors associated with MSK disorders of the hand & wrist
• Mono-Task Work for ACGIH-TLV for Hand Activity

  • Hand, wrist, & forearm, for one side at a time
  • 4 or more hours per day
  • Repeatedly performing a similar set of motions or exertions
  • Short Cycle Tasks
  • Not good for multi-tasks, only mono-task handwork)
• ACGIH-TLV Risk Score Basis

  1. Hand Activity Level (HAL) from Latko
  2. Normalized Peak hand Force
• ACGIH-TLV identified combinations of HAL & peak force where hand/wrist/forearm MSDs are likely in many people, possible in many people, or unlikely in most people
• Strengths of ACGIH-TLV

  • Easy to use
  • 2018 Activity Level & TLV based on epidemiological data
• Limitations of ACGIH-TLV

  • Linear curves not consistent with biological tolerance data
  • 2018 TLV & Activity Level are very conservative
• 2 Inputs for DUET

  1. Repetitions
  2. Stress: estimated using OMNI-RES scale
• DUET estimates cumulative damage for combined upper limb tasks & is based on the idea of material fatigue failure
• Strengths of DUET

  • Can evaluate exposures associated with multiple tasks
  • Only requires 2 inputs per task
  • Based on material fatigue from in vitro stress/strain tests of tendons
• Limitations of DUET

  • Doesn't account for duration
  • Doesn't account for rest/recovery or posture
• Quick Exposure Check

  • Assesses exposure of 4 body areas at greatest risk for MSDs
  • Involves ergonomist & workers opinions/perceptions
  • Useful to quickly identify hazards
• QEC: Back Posture (A1-A3)

  • A1 = Almost Neutral
  • A2 = Moderately flexed, extended, twisted, or side bent
  • A3 = Excessively flexed, extended, twisted, or side bent
• QEC Back Posture (B1-B5)

  • Select one option of the following
  • B1-B2 = Stationary Task
  • B3-B5 = Lifting, Pushing/Pulling, Carrying Tasks
• QEC Wrist/Hand (E)

  • Based on most awkward wrist posture: flexion/extension, ulnar/radial deviation
  • E1: almost straight (<15º)
  • E2: deviated or bent (>15º)
• QEC Wrist/Hand (F1-F3)

  • Refers to movement of wrist/hand & forearm, not fingers
• QEC Neck (G)

  Excessively bent or twisted refers to angles >20º with respect to the torso
• QEC Shoulder/Arm (C1-C3)

  • Based on position when shoulder/arm is most heavily loaded
  • May be different time than when back was assessed
• QEC Shoulder/Arm (D1-D3)

  Shoulder/arm movement frequency
• QEC Worker's Assessment: Maximum Weight Handled (H)

  • Weight borne by worker, not handled by equipment
  • Can supplement by measuring loads, but don't replace worker's assessment
• QEC Worker's Assessment: Time Spent on Task (J)

  On average, the amount of time the worker spends on the task being assessed
• QEC Worker's Assessment: Maximum Force Level (K)

  • Max force for one hand only, even if 2 hands are used
  • Can supplement with measurement
• QEC Worker's Assessment: Visual Demand (L)

  • Low = almost no need to view fine details
  • High = need to view some high details (need to elaborate)
• QEC Worker's Assessment: Driving (M)

  • Investigates whole-body vibration resulting from driving
  • If worker doesn't drive, select M1
  • Doesn't include driving to/from work
• QEC Worker's Assessment: Vibration (N)

  • Hand-arm vibration from using tools
  • If no vibrating tools used, select N1
• QEC Scoring

  • Compare level of exposure between body areas
  • Identify where exposures are highest to prioritize action
  • Compare level of exposure before/after an intervention
  • Not enough epidemiological evidence to interpret injury risk associated with certain scores (use for comparisons)
• QEC Score Interpretation

  • Low exposure scores could have 1-2 interactions with a high score
  • Moderate, high, & very high indicates there are likely several interactions that should be identified & reduced