Proper body alignment

| July 08, 2008

Growing sophistication in driver comfort research means fewer backaches at the wheel.

Because you sit for long periods while being jostled by bumps and vibration, yours is one of the leading occupations for back injury and pain, according to the American Physical Therapy Association. Sitting can be downright dangerous to your back. Truck manufacturers and seat designers feel your pain. They use on-road testing, computer modeling and ergonomic design to build seats that are comfortable and responsive.

They also work closely with drivers. “We will go back and forth with drivers over the course of a couple weeks of driving and ask about the comfort of the seat and the cab,” says Josef Loczi, manager of Human Factors and Interior Concepts at Daimler Trucks.

Researchers are also using computers and special “human modeling software” to create statistical models and three-dimensional representations of drivers that reflect driver needs, requirements and behavior. At the Human Motion Simulation Laboratory at the University of Michigan, researchers developed “digital human models” that are three-dimensional human avatars that look like drivers. “An in-cab designer will set up these figures using our posture prediction models to represent drivers of different sizes and shapes,” says Matt Reed, research associate professor in the biosciences division of the University of Michigan Transportation Research Institute. “Then they conduct ergonomic analysis looking at clearance and vision and use that information to determine how much seat adjustment range and steering wheel adjustment range is needed and if there’s enough head room, among other things.”

Reed says the result is that vision out of the cab, clearance and accommodation for the driver has improved substantially through the use of ergonomics.

Like so many drivers, Mark Kroger suffered from a back injury. His pain originated with a herniated disc injured in a fall. Finally, last summer he bought a new seat for his 2005 truck in the aftermarket. “Buying a better seat was a good move for me to make,” says Kroger, an owner-operator from Amarillo, Texas, leased to Seaboard Transport. He also bought an aftermarket mattress for his 72-inch sleeper.

Researchers and designers at Commercial Vehicle Group employ computer modeling and simulators in developing truck seats for its National Seating brand. Its computer model incorporates elements of a truck’s seating system and suspension with external factors to find ways to reduce the jolts and vibrations that are most harmful to the body.

“We have a whole catalog of road inputs and various terrain that we introduce into computer models,” says Logan Mullenix, vice president of research and development for CVG. “We take it a step further with a driving simulator that includes the full vibrations found in a truck.” All this enables the manufacturer to get verified test information into the design of its seats much quicker than in years past.

“Pressure mapping of many different drivers helps in the development of cushion shapes to support different body sizes,” says Jim Bechtold, assistant chief engineer at Kenworth Truck. “Computer-generated figures of various sizes can be placed in a virtual cab model,” and the visibility of dash-mounted gauges and the reach to dash switches can be studied.

Seat crafters are dealing with the fact that drivers are taller and weigh more than their predecessors 20 years ago. “We’ve had to make seats wider,” says Larry Blankenship, director of product development for CVG. “Twenty years ago, the standard seat was 18 inches wide,” he says. “Now the standard is 20 inches, with an option to go out to 22 inches.”

A new seat can only help so much, though. Mike Skurdahl’s back would get stiff from hours of driving. He blamed it on an injury suffered decades earlier. And his shoulders ached from holding the steering wheel. He found relief by lifting weights and running. “The shoulder soreness went away, and the lower back pain is all gone, too,” says Skur

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