In this study, an employee lifted a heavy drum using three different techniques.  In Lift 1, he carried the drum to a dolly.  Lift 2, he moved the dolly to a better position, so the lift was direct.  Lift 3 involved lifting a drum over another drum.

This analysis shows the loads on both the shoulders and on the back.  Lift3 creates a whopping 1004 lb. load on the back.  Time differences that appear insignificant on the plant floor reveal themselves as meaningful with formal study — in this case, Lift 3 takes 40% longer.  As a final note, this method captures the strain from carrying the load in addition to lifting it, which is evident in comparing Lift 1 with Lift 2.

Example 5: Resolving a Labor-Management Dispute

This example is from a company that inspects and repairs boxes and other small containers for a major distribution company.  The union had complained that the work was too fast and should be slowed down.  Management claimed that slowing down the work economically unfeasible.

This task involved two stages: inspecting and stacking the containers (A in the graph above), then straightening and reorienting the stack and carrying it to a pallet on the floor (B above).  The argument had been about the time it took to perform step A.   However, the analysis clearly showed that part B was the demanding activity that was causing the exertion and fatigue.

Moreover, it was possible to eliminate all of part B by purchasing a pallet lift and stacking the containers directly onto the pallet.  This made about one-third more time available, both for more rest and for more production.  Thus more containers could be inspected with less effort and resulted in a win-win solution.

Caveat — “Safe” Limit

As a final note, I generally do not use this method — or any method — to determine if a job is “safe” or not.  I’m generally more interested in looking for ways to improve any job, since even if a particular situation has low risks for injury, there may still be inexpensive ways to make it more efficient and easier to do.  Furthermore, the scientific studies haven’t yet identified precise “safe” levels for loads on the shoulders, elbows, or wrists (although such evidence exists for the lower back).

However, this method may end up being a good tool for this purpose.  It provides a good way to capture a lot of information on the physical demands of specific tasks, which then can be compared to numbers of injuries associated with those tasks to help find out what is in fact “safe” and “unsafe.”

A good general rule for practical ergonomics is to play down measurement systems.   If the goal is to solve problems, rather than merely documenting them, it is much more valuable to get in the habit of simply watching videos of jobs and focusing on brainstorming improvements.

However, from time to time, you may need to quantify the physical demands of a task.  Numbers have power and you may need them to convince others of the need to take action.  Furthermore, sometimes the problems aren’t so obvious and you can benefit from a closer, more detailed look.

Contact Dan for complete directions and a template to facilitate analysis: dan@danmacleod.com or (570) 242-4664.

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*The original concept for this method was developed by Peter Holzmann, Ph.D., based on his own proprietary scoring system, which I found too complicated for practical use.  I subsequently tried the Rapid Upper Limb Assessment (RULA) scoring system, then realized that biomechanics provided an even better approach to characterizing physical demands for this purpose.  The biomechanical models developed at the University of Utah for the shoulder and back provide the best system I have found for this use.