Lower back pain is the second most common reason for a doctor visit, and costs the supply-chain industry around $100 billion per year. One of the leading culprits for this pain and expense is the pushing and pulling that occurs in the hundreds of thousands of distribution facilities throughout the world.
Thousands of employees injure themselves each year because of some sort of pushing activity with industrial equipment. It’s clear that we’re not doing enough to solve this problem. However, we are seeing improvements in measurement standards for equipment that’s involved with pushing.
Over the years, companies have become more heavily focused on push-related activities for two reasons: better information and statistics concerning injury have become much more common and accurate, and institutions like OSHA have highlighted employee safety and a company’s role in protecting its employees. Thus, equipment performance has become more important than ever, because upgrading equipment is the fastest and easiest way to reduce push/pull by significant percentages.
When a company makes a sizeable investment in equipment, it’s critical to verify that the purchase was worth the money and effort. The full return on investment comes over time, but the quickest way to confirm an immediate improvement in push/pull is by measuring the push/pull force. For years, the standard way to do that has been with a handheld force gauge. This device allows individuals within a company to push a cart and determine what the force is before and after an upgrade in equipment. This is a critical step in any ergonomic initiative that a company may run.
There is, however, a huge challenge with measuring push/pull. The amount of force that someone encounters while pushing a cart depends on the person doing the pushing. That means that human error is a major obstacle in getting accurate readings before and after new equipment has been employed. In particular, the speed a person applies to the force gauge influences the measurement dramatically, and can be a greater factor than the weight of the cart. We have conducted tests where we got 10 times higher or lower push/pull force simply by changing how fast we pushed the cart — from, for example, eight to 80 pounds.
There’s a fairly easy solution to such unpredictable and varying results: use a consistent push/pull standard every time you do a measurement. For example, push the cart one meter in four seconds to start, then one meter every one second after that. The key is to account for distance traveled over time. If you do this in the same place and under the same conditions, you will always know if a piece of equipment has made a push/pull improvement, because each piece of equipment has been measured with the same guidelines.
The standard for this measurement process has been International Organization for Standardization (ISO) 11228-2. This is still an excellent standard for comparing equipment, mainly because it’s consistent. If companies aren’t using a standard, they’re almost certainly not getting consistent measurements, unless it’s by sheer luck. For this reason, companies should feel comfortable using the ISO standard if they’re interested in comparing equipment push/pull outputs.
However, we need to think about push/pull measurement from another angle. Remember our biggest goal is to reduce push/pull, but we lower it in the first place to reduce stress, injury, and costs. ISO 11228-2 allows us to compare equipment consistently, but does it necessarily tell us anything about the speed at which a person in a factory is actually pushing? This is important because if we are pushing a cart more slowly in testing — compared with the rate of an average person in a factory — our push/pull force numbers are artificially low. Remember you can manipulate the force by how fast or slow you push a cart (slower/lower, faster/higher). For this reason, the test speed should match the speed of an actual person. In this way, measurement standards line up with injury risk, while also allowing us to compare equipment performance.
We recently collaborated with The Ohio State University Spine Research Institute on a study — currently yet to be published — on push/pull standards. One part of the study had test subjects push a cart at their own self-selected speed. What they found is that this corresponded with a faster testing speed that they used later (one meter in three seconds initially, 0.5 m/s sustained).
This testing speed was faster than the current ISO standard. In other words, we should conduct push/pull testing at this faster speed to best match the speed at which our employees are pushing. This will most accurately gauge their real injury risk. If you want to verify this in a less scientific way, then just measure the speed over distance of a few people in your organization, pushing carts with weight on them. This will give you an idea of how much more accurate the new standards are at gauging injury risk.
These latest study results are an important piece of the puzzle in protecting valued employees, while at the same time reducing the total cost to businesses throughout the world. Is everyone going to push at the same speed? Probably not, but from what we can tell, this new standard is far and away the most scientifically verifiable push/pull measurement approach for approximating the speed at which real people actually push a cart. So, by using this guideline, we can better accomplish our goal of eliminating stress and injury, while also reducing costs to the business.
Joseph Lyden is president of Caster Connection, a manufacturer of casters and wheels based in Columbus, Ohio.
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