Even though the time spent on farm equipment might seem less physically taxing than other jobs on the farm, sitting on a vibrating piece of machinery for long periods of time can actually amplify the driver’s other aches and pains.
Operating nearly any farm vehicle causes the driver to experience Whole Body Vibration (WBV), which occurs when the shaking motion of the vehicle is transferred to the body of the operator. Back pain is one common ailment linked to WBV.
Recent research funded by the Great Plains Center for Agricultural Health at the University of Iowa measured levels of WBV in various farm vehicles. Dr. Nathan Fethke, associate professor of occupational and environmental health and principal investigator on the study, found quite a bit of variation between different vehicles and the WBV experienced by the operator.
WBV starts with the contact between the vehicle tire and terrain. That impact is transferred through the vehicle frame and seat to driver. The vibration that the operator experiences varies depending on the vehicle and seat type, the speed and the type of terrain.
In general, someone driving a heavier vehicle equipped with a built-in-suspension seat experiences lower amounts of WBV than a person driving a light vehicle equipped with a seat bolted rigidly to the frame. And, for the most part, the faster the speed, the greater the vibration.
But a sudden change in terrain, such as driving over an obstacle or hitting a low spot in the ground, can cause sudden vibration spikes (or “mechanical shocks”) similar to those experienced during collisions in football or other contact sports.
Dr. Fethke’s research team traveled to farms throughout the Midwest and attached sensors called accelerometers to over 100 farm vehicles, from combines to ATVs and fork trucks, to measure WBV levels during actual farm work.
To calculate a recommended limit for farm vehicles, Fethke used European Union standards and had to account for the wide variation in tractors, skid steers, ATVs, combines, and all the other vehicles tested.
ATVs tended to be the worst offenders, and 50 percent of the ATVs studied reached the EU exposure limits for WBV before four hours. Combines, in contrast, reached the exposure limits well after eight hours of continuous operation. Tractors and utility equipment fell in the middle at about six hours.
But, Dr. Fethke notes there was significant variation among the tractors measured.
“The reality is, at least in our data, factors such as vehicle type, make, model and year of manufacture were poor predictors of WBV levels. Other than combines, the variety of vehicles our participants used to accomplish similar tasks make it difficult to suggest specific recommendations that apply to everyone,” he says.
Even when WBV levels are low, Dr. Fethke says long hours of continuous operation can fatigue back muscles. The researchers recommend taking breaks to stretch muscles and avoid lifting heavy objects immediately after long periods of vehicle operation.
[Photo: Dr. Nathan Fethke]