Many of the approaches we currently use for ergonomics evaluation & risk assessment may soon be obsolete. You may be thinking … “No way! I’ve been using the same ergo risk assessment & evaluation tools for the last 10-15 years.”. If that's the case, keep reading …
This post outlines a different, emerging approach … individualized ergonomics evaluation.
Traditionally, approaches to ergonomics evaluation & risk assessment have consisted of evaluating with respect to limitations & characteristics of a defined population. For force-based ergo evaluation & risk assessment, this is typically accomplished by choosing a specific population strength capability. For example, evaluating grip strength with respect to the 10th% or 25th% female grip strength capability. If we keep job demands below this 10th% female strength capability, then at least 90% of females will have sufficient strength to perform the job, as will nearly 100% of males. This approach accommodates the vast majority of the workforce. From a design standpoint, this makes perfect sense. But the shortcoming occurs in the application, particularly with respect to ergonomics risk assessment.
Ergonomics risk assessment typically involves “rating” jobs (or tasks) with respect to risk of injury. This often results in output metrics that group or categorize jobs based on rated injury risk ... Low, Moderate, and High (usually with the anticipated green, yellow, and red color coding).
When using ergo risk assessment tools calibrated for weaker members of the worker population (as in 5th% or 10th% female strength) it is not uncommon for a facility experiencing relatively few injuries to have a significant percentage of jobs rated “high risk”. I have witnessed facilities with outstanding (VERY LOW) work-related injury/loss statistics have as many as 50-75% of jobs rated “high risk” by conventional ergo risk assessment tools. This results in undesirable outcomes …
Identifies an unreasonable number of “problem jobs”
Flagging a high percentage of jobs as “high risk” can make ergonomics improvement efforts appear to be Mission Impossible.
Distorts the perception of injury risk
What does “high risk” really mean if we experience few injuries, but we have a lot of “high risk” jobs? This makes little sense.
Erodes the credibility of the ergonomics process
Let’s face it, if there are few injuries occurring; then it is highly unlikely that the jobs are truly “high risk” for the actual worker population. When this occurs, the ergo risk assessment tool begins to lose credibility with managers and even front line employees.
The reason why this sometimes occurs - few injuries, yet a high % of high risk jobs - is due to something I call failing to achieve "population relevance”. This occurs when the ergonomics risk assessment tool is calibrated for weaker members of the workforce, yet the actual worker population is, on average, substantially “stronger”.
For example, a conventional ergo risk assessment tool may indicate that a hand force is “high risk” (based on 10th% female strength capability). For someone with a strength level below the 10th percentile female strength level, this hand force may indeed be “high” and result in increased injury risk, muscle fatigue over the course of the shift, etc. But if the worker actually performing the job (NOW) is a female with 75% female strength capability, the reality is that this job may not pose a problem … despite the “high”/red risk rating. The factor of significance in this example is the individual’s strength … which, like it or not, is a relevant variable in determining injury risk, predicting muscle fatigue, etc.
A proposed solution …. INDIVIDUALIZED ergonomics evaluation. By all means continue to DESIGN for weaker members of the workforce (10th% female strength, 25th% female strength, etc.). To do so is a good thing! But, conduct ergonomics evaluation & risk assessment for the individual. Yes, I said it. It just came out! Evaluate and conduct risk ergo assessment for the INDIVIDUAL. Get ready to wrap your brain around a different approach/perspective.
I realize that on the surface this concept of individualized ergo evaluation may seem foreign, especially since most of us have been taught to ALWAYS design for weaker members of the workforce. Allow me to explain why evaluating work with respect to the individual is more practical than you might initially think.
First, a short explanation of individualized ergonomics evaluation. I define individualized ergo evaluation as factoring in the individual characteristics of the worker as we go about conducting ergonomic evaluation or risk assessment. For force-based evaluation, this consists of using individual strength capabilities as model inputs. This can be accomplished by measuring individual strength directly - measure each employee’s strength capability for grip strength, pinch strength, etc. Feasible, but a hassle! A more practical option is using predictive equations to accurately estimate individual strength capabilities. Saturn Ergonomics is developing individualized ergo evaluation technology for “calibrating” evaluation tools for the individual. Model calibration utilizes readily obtainable inputs such as gender, age, height, and bodyweight.
Individualized ergo evaluation approaches allow looking at the evaluation results from either the individual perspective, or from the perspective of the group (line, department, plant, etc.). The individual perspective may be most useful for applications such as incident investigation, making alternative duty job assignments, etc. In these cases, we need to understand how individual strength capability matches up with actual physical demands of the job. On the other hand, looking at ergo eval or risk assessment from the group perspective would be a better choice for things such as determining priority for making ergo-related improvements (one reason for “risk assessment”), allocating resources for ergonomics training, making spending decisions for ergo-related solutions, etc. For these things, we are more interested in how the worker population (as a whole) matches up to the physical job demands of work in the area of interest. Either way work is evaluated with respect to the individual, but aggregate exposure metrics calculated (electronically) for a line, department, or plant.
Individualized approaches to ergonomics evaluation and risk assessment have the potential to help prevent the common scenario of “we have no injuries, but a high percentage of our jobs are high risk”. The individualized evaluation approach should more accurately identify where there is a true “gap” between job demands and the actual physical capabilities of the workforce.
We live in an age when there is value to having more information (rather than less). Individualized ergo evaluation provides MORE information! And will provide greater fidelity in our efforts to evaluate, prioritize, and measure all things ergo-related. Also, we live in an age where computers & software makes short work of what used to be tedious calculations performed by hand. Modern software-based solutions enable us to do more than we could in the past … with our paper (or electronic) forms, tediously applying 15-20 year old eval models & risk assessment tools.
Another critical factor is that emerging ergo evaluation technologies may very well REQUIRE individualized evaluation. This is particularly true for new posture-based, dynamic force evaluation models. For example, Saturn Ergonomics is currently involved in the development of a practical, dynamic shoulder evaluation model that takes into account both arm/segment weight and object weight. Without individual model inputs - needed for the model’s algorithm to calculate arm/segment geometry & segment weight - this type of model is not even feasible. Evaluating work with respect to the individual, if it enables us to evaluate things more accurately or enables us to evaluate things we couldn’t evaluate before, is a good thing.
I believe that the day is rapidly approaching where it will be much more common for ergonomists to evaluate work with respect to the individual. This will enable us to make better decisions for the individual, and make better decisions concerning the worker population as a whole. When you hear the term “individualized evaluation”, please appreciate that this is progress. Individualized ergonomics evaluation will enable us to be more effective applying ergonomics.
Murray
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