How to interpret “occasional” in a PDA

If you’re just getting started with completing Physical and Cognitive Demands Analyses (PCDAs, also known as PDAs, PDDs, or JDAs) in your facility, you’re probably casting around for a good template. Some of the ones that are publicly available include: Something that you’ll notice about these templates is that they report exposure to certain demands in terms of frequency categories. WSIB’s form reports demands as:
  • Not at all (stays in the same position)
  • Occasionally (no regular motion)
  • Frequently (regular motion with pauses)
  • Constantly (continuous motion)
OHCOW’s form reports demands as:
  • Never
  • Rare
  • Occasional
  • Frequent
  • Constant
WSPS’s form reports:
  • Not required
  • Rarely (<2%)
  • Occasional (3-33%)
  • Frequent (34-66%)
  • Constant (67-100%)
We’ve also looked at various insurance company job demands summaries, and they each use their own criteria. Canada Life’s form reports:
  • Never
  • Sometimes
  • Occasional, less than 1 hour per day
  • Frequent and/or repetitious for 1-3 hours daily
  • Maximum job requirement for over 3 hours per day
Government of Canada’s form reports: For lifting, carrying, walking, climbing, driving, reaching, bending and kneeling
  • 0%
  • 1-25%
  • 26-50%
  • 51-75%
  • 76-100%
For sitting/standing, and driving at one time:
  • 0-30 minutes
  • 31-60 minutes
  • 61-90 minutes
  • More than 90 minutes
On an average day, sitting, standing or driving:
  • 0-2 hours
  • 3-4 hours
  • 5-6 hours
  • 7-8 hours
Sunlife’s form uses the same criteria as the Government of Canada, above, but adds a few demands, including reaching above, at, and below shoulder height, daytime and nighttime driving, etc. Some of our clients use insurance providers whose forms are not available online, so let me assure you that there are additional “definitions” for various frequency criteria. If you, like me, need numbers to be interpreted “literally”, you’ll immediately become alarmed that the thresholds provided for these “frequency” categories are defined as “durations” not “frequencies”. If I say to you that I bend to pick up a sock in my laundry room “occasionally”, you might wonder if that means 3 times per load, or only once. If I respond that I mean 20% of the time, you’ll still not be sure if that means that I spend 20% of my laundry time bent over, or that I drop 20% of my socks. Our PCDAs have never used terms like “frequent” or “occasional”, mainly because we summarize physical demands in terms that align with the WSIB’s Functional Abilities Form, and the only frequency quantifier required there is “repetitive” movement of various body parts. For a repetitive job like “soup station” or “palletizer” we actually count how many awkward back, shoulder, elbow, neck and wrist movements the worker performs, and we report these in “per minute” units. When assigned to Station 2 on the “Thigh” line, the worker performs 3.3 right wrist movements, 0.5 right shoulder movements, and 2.1 neck movements per minute. On our summary page, we categorize the demands as “repetitive” if the movement frequencies exceed certain identified thresholds. (See our summary document here.) For a non-cyclic job, we identify whether the worker is exposed to repetitive demands for any of the duties performed. Of course, clients who use our PCDAs for non-work-related claims management have often asked us whether the demands are “occasional” or “constant” and we have patiently explained why we don’t use those categories. Until recently. We have just rolled out a new PCDA template, built in Excel. It calculates the percentage of the job cycle (typically a full “day”) that the worker is exposed to each demand. We’ve invested over 100 hours into creating this new template, so, for now, we’re going to use it for our projects, but we are not going to license it for other clients to use. For a cyclic job with a cycle of 1 minute, if right shoulder demands are repetitive all day, the exposure to repetitive right shoulder demands would be 100%, and we would categorize that as “constant”. Cyclic jobs, where a worker does the same thing over and over all day long, have always been relatively easy to interpret, so the real value added by this approach is for the non-cyclic jobs such as Personal Support Worker or Mechanic. For these jobs, the ergonomist meets with workers and supervisors to estimate the duration of each duty, creating a “big picture” of how the day (or week) is spent. (For example, on average, the Line Technician spends 1 hour per shift performing quality checks, 0.5 hours troubleshooting issues, and 6 hours monitoring production.)  The ergonomist then measures the duration of each task, and then identifies which tasks require each demand (walking, repetitive wrist bending, repetitive neck twisting, etc.). The spreadsheet calculates, for the summary page, which demands are “rare”, “occasional”, “frequent” etc. We can change the thresholds to align with whatever your insurance company needs. As always, objective, consistent, science-based reports are our priority. Our new reports include both an insurance summary (for your insurance provider) AND a WSIB Functional Abilities summary, so you can use the PCDA for either type of claim. Interested? Contact

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