UI Study: Machine vibrations may contribute to farmers’ back pain

When a farmer complains of lower back pain — especially during the peak of harvest season — it’s no joke.

A new study from the University of Iowa has found that vibrations from farm machinery may lead to increasing back pain for farmers and other agricultural workers.

After examining vibration levels in several types of agricultural machinery, the research team from the University of Iowa College of Public Health found that farmers’ exposure to these levels for a long period of time can lead to negative musculoskeletal health outcomes, such as lower back pain.

“Something like back pain, it’s not just a nuisance,” said Nathan Fethke, lead investigator on the study and associate professor at the College of Public Health “It affects a lot of people.

“We want it to not be just part of the job. We want (back pain) to be something farmers are thinking about early in their careers so they do what they can to protect themselves.”

According to the study, whole-body vibrations is common for agricultural workers. Farmers can be riding a tractor, for example, for long hours at a time — including during the harvest season, when they’re using equipment from sunrise to sundown.

Researchers said spending many hours on these machines at a certain rate of whole-body vibrations can increase the frequency of back pain episodes. But little is known about the “characteristics of exposure experienced during actual production practices,” the study stated.

UI researchers attempted to measure that.

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The study, released in the research journal “Annals of Work Exposure and Health,” examined whole-body vibration levels — defined as mechanical vibrations transmitted to the human body through a contact surface, such as a seat — in 112 machines, including combines, tractors, skid loaders, forklifts and all-terrain vehicles, “as more than 50 Midwestern farmers went about their daily routines,” according to a study summary.

Fethke said vibration levels were compared to the European Union’s whole-body vibration exposure limits, a regulation that limits vibration exposures based on “action levels,” or the maximum amount a vibration a worker can be exposed to in a day without risk.

Researchers measured the vibration levels of the machines themselves, and how effective the seats were in reducing vibration levels to the operator.

What they found was that 63 machines, or more than half measured, had sufficient vibration levels to reach the European Union’s action level within eight hours of continuous use.

Researchers found all-terrain vehicles, heavy utility vehicles and tractors “were more likely to reach the action value within eight hours than those from combines and miscellaneous vehicles,” the study stated.

Combines, however, brought different results. Among the 18 combines measured in the study, “not one would reach the action level in eight hours” — most likely due to their mass, Fethke said.

Tractors in particular did not fare well, as the seat-based suspension systems did not reduce whole-body vibrations, according to the study summary

“It is possible that these suspension systems were not properly adjusted to the weight of the operator, or had degraded over time from mechanical wear and tear,” Fethke said.

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Of the 112 machines observed, about 35 percent were manufactured after 2000. The majority, roughly 65 percent, were manufactured before 2000 — and about 15 percent of those were built before 1969.

The amount of time farmers spent on these machines “is also a key factor,” Fethke said.

“Ultimately, a person’s ‘daily dose’ of vibration is a function of both the magnitude of the vibration and the overall exposure time,” he said.

“This can be tricky to sort out, particularly since farmers often use multiple machines in any given day. Each machine, and the time it’s operated, will contribute to the daily dose.”

Fethke and the other researchers on the study recommend farmers check seat suspension systems during the low seasons to make sure they are working properly.

The seat should be adjusted to the operator’s body weight and should not “bottom out.”

If this is the case, owners should consider a replacement. A seat cushion will not help reduce vibration levels, Fethke cautioned.

“Long hours on vibrating machinery can be fatiguing for the back,” Fethke said. “One potentially useful prevention technique is to avoid physically demanding activities (such as lifting heavy objects) for a short time after exiting the machine.

“This may allow the back to recover a bit before additional demands are placed upon it.”

The study was conducted under the Great Plains Center for Agricultural Health, a center founded in 1990 within the University of Iowa College of Public Health.

According to its website, the center assesses the health and safety needs of agricultural workers in Iowa, Missouri, Kansas, Nebraska, Illinois, Wisconsin, Minnesota, South Dakota and North Dakota.



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