Week 5 Readings Flashcards
What type of methodology has this study used to determine TLVs ?
Threshold limit values
Time weighted average methodology to account for multi-task jobs
Time weighted average TLV for HAL was a good predictor for wrist tendinosis
What is OR and what does it mean?
Odds ratio: ratio of the odds of an event occurring in one group compared to the odds of the same event occurring in another group
For the wrist tendinosis study, what was their inclusion and exclusion criteria and why did they choose this protocol?
Eligible participants: hand-intensive manual work and engaged in 4 or less tasks
- Excluded new workers or workers that anticipate leaving job (prospective study)
- Excluded workers that spent a significant time doing office work or driving a forklift
How did the researchers determine exposure to forceful and repetitive hand exertions?
Ergonomists estimated weekly hours for each primary work task based on in field observation and video recording.
If they were unable to perform individual exposure assessment for a subject, exposure levels were imputed based on median values of participants who performed same task
Time weighted average of each exposure variable was calculated for each participant by weighting the exposure variable for a task by hours worked on that task per week
What is the:
- ACGIH_TLV HAL
- JSI
American Conference of Industrial Hygienists Threshold Limit Value (ACGIH-TLV) for Hand Activity Level (HAV)
- Combines individual risk factors in formulas or indices
- Quantifies exposure to force and repetition for mono task jobs
- Improves the prediction of upper extremity MSD over individual physical risk factors
- Quicker and easier to apply than video analysis methods used to quantify repetition
JSI: job strain index
- Must measure 6 factors making it more time consuming than ACGIH-TLV for HAL
- Strain index was calculated using efforts per minute, speed of work, and posture, self-report identification of task duration, and intensity of effort, and video analysis of duration of exertion while in heavy pinch or power grip
Both are tools for safety professionals to quantify risk for distal upper extremity disorders based on exposure to more than one biomechanical risk factor such as force, repetition, and posture
How did they account for workers doing multiple tasks?
Time-weighted average methodology to account for multi-task jobs
Made calculations to estimate average exposure of a worker to hazardous substance over a period fo time.
How did they determine “repetition”?
Observer rated tool: HAL which is a categorical scale from 0-10
Observer rated speed of work
Video analysis of heavy pinch or power grip and total repetition rates: Repetition was determined to be repetitions of hand exertions per minute. Exertion was defined as a readily observed movement of the wrist or fingers or a change in the load to the hand
How did they determine psycho social stressors?
Used job content questionnaires and job content scales included physiological demands, skill discretion, decision latitude, decision authority, coworker support, and supervisor support
What personal factors increased the wrist tendonitis incidence rate?
Female gender, hispanic ethnicity, and working day shifts were associated with higher hazards for wrist tendonitis
Medical conditions: diabetes, thyroid disease, rheumatoid arthritis, lupus, gout
What was the “surprising finding” related to repetition rate?
Regardless of method used, repetition showed no predictive factor for right wrist tendonitis
When adjusting for force, measured by the % time in heavy pinch, a protective pattern for repetition emerged
What challenges did they find with the JSI for predicting wrist tendinosis?
Although it almost perfectly predicted all those who would develop wrist tendinosis, it was not very specific in identifying those who were not at risk for developing wrist tendinosis
What are some of the limitations of the study and why are they important for interpreting the results?
- Possible source of error is self-reported worker estimates of weekly time spent on each task
- number of cases of right wrist tendinosis was relatively small so it is possible that some of the exposure variables that were not statistically significant with the outcome were a result of inadequate power.
- 7 people did not describe their pain to work exposures and thus data from them could not be counted as a case
- Workers might choose to take on more demanding jobs based on their own preferences, abilities, or motivations, rather than being randomly assigned or placed into those roles. Results in selection bias.
What is the main significant finding for practitioners from this study?
- The % time spent in a heavy pinch is an important risk factor for wrist tendinopathy
This study highlights the singular importance of duration of exposure to high force pinch in the development of wrist tendinosis
Threshold limit values for preventing workplace wrist tendinopathies
