EYE ON ERGONOMICS: Mowing Pains

Mowing lawns can be a bone-rattling experience. At some point, every landscape contractor has bounced over protruding tree roots, bumpy rock-hard soil or fallen tree branches. Whether on a riding, walk-behind or stand-on mower, vibrations and repetitive motions can cause short- and long-term physical effects.

Though more mowers today are being built for comfort, little research is available on how ergonomics affect the landscape industry. "The landscape industry is very uninformed of ergonomics," says Brian Roberts, director of ergonomic services, CNA Financial Corp., Chicago, Ill. "They look at it and say, ‘How can that apply to me?’ I think the first thing contractors have to do is educate themselves and ask for help to begin understanding ergonomics and cumulative trauma."

ERGONOMICS EDUCATION. When it comes to ergonomics, the landscape industry is about 25 years behind manufacturing, according to Roberts. The National Institute for Occupational Safety and Health (NIOSH), which is the federal agency responsible for researching prevention of work-related injuries, has studied the effects of heavy mining and farming equipment on operators, but no information is available on landscape equipment, according to Thomas Waters, supervisory safety engineer, NIOSH.

"NIOSH is the research arm of OSHA (Occupational Safety and Health Administration), and if they’re not doing research, there’s not a whole lot of research you’re going to find on it," Roberts says, adding that research may be lagging in this area because landscape contractors and associations haven’t embraced ergonomics as a necessity.

Landscape contractors may want to pay more attention to how ergonomics affects their operations because back injuries can cost a company anywhere from $500 to $1 million depending on severity, Roberts says. That includes workers’ compensation costs and indirect costs, which are typically four times the direct costs, according to Roberts. In other words, a $10,000 back-claim injury may cost a contractor $50,000 in the end. Indirect costs include hiring a replacement worker and lost productivity and efficiency, Roberts explains.

Insurance rates can also increase if a company has a long history of injuries, Roberts says. A company with few injuries may have an experience modifier of 60 percent, which means that contractor will receive a 40-percent break on the standard premium. A company with several injuries could have an experience modifier of 110 percent, which would equal the standard rate plus 10 percent, Roberts explains.

FIT FOR COMFORT. Manufacturers have made strides toward helping contractors reduce these ergonomic-related costs. They’ve modified equipment to lessen the strain caused by vibration and other movements. The most vulnerable body parts to aches and pains during extensive mower use are the hands, wrists, forearms, back and legs. In the landscape industry, mower vibration is often the culprit for back injuries.

"If you’re going over any bumpy terrain or uneven surfaces, it’s going to create a jolt or a jar, and that can create large impact forces that are transmitted right up the spine," Waters says. These repeated jolts sometimes force the spinal disks to rub together resulting in nerve irritation, Waters adds.

Full-suspension seats with shock-absorption qualities can reduce the chances of back and nerve problems associated with excessive vibration. "There’s really not any hard numbers or solutions other than to try to get a tractor that has good vibration-absorption qualities or has good seats that absorb a lot of vibrations, and try to use anti-vibration shocks," Waters explains.

With some full-suspension seats adding $300 to $400 to the cost of a mower, slight enhancements in comfort may not sway all contractors. "It can’t be uncomfortable,"says Kevin Lund, commercial mowing product manager, John Deere, Moline, Ill. "If it’s uncomfortable, or if there’s particularly bad visibility, that’s going to be a problem. But if it’s reasonably comfortable, it’s hard to say that there’s someone with a particular advantage. In other words, I don’t see operators paying a lot more for a machine that’s a bit more comfortable."

Vibration is broken down into two categories: segmental and whole-body. Whole-body vibration is usually associated with riding mowers because the vehicle distributes vibrations through the entire body. Segmental refers to localized vibrations in areas such as the hands or arms. This type of vibration is more common with hand-held equipment.

Mower manufacturers are now designing shock-absorbent seats to lessen the impact of vibrations on landscape contractors. In the past, seats were supported by a metal pan with a back cushion and a seat cushion consisting of foam and metal springs. Now, several mower manufacturers have added a shock-absorbent spring device that is adjustable by turning a knob, says Deven McGhee, project engineer, Encore Manufacturing, Beatrice, Neb.

"Operators are asking to go faster and faster all the time," McGhee says. "Well, the faster you go the harder some of those jarring movements are going to be because you’re hitting at a higher speed. So you’re trying to combat that with better seats and full suspension to try to take away from some of that jarring."

Some mower seats now even consist of an elastic material that helps dampen vibration, according to Garry Busboom, director of engineering, Exmark, Beatrice, Neb.

"We’ve gone to a different type of seat suspension that is an elastomeric material – it’s not metal springs, and what that does is it reduces the vibration that’s transmitted through the seat to the operator," Busboom says.

Full-suspension seats can raise the cost of a mower by 3 to 4 percent or an additional $360 to an $8,000 mower, according to McGhee. There are also add-in suspension seats, which contain a shock-absorbent system placed between the frame and board instead of being built in like the full-suspension seats.

Seats today are also equipped with adjustable armrests that provide a bridging point between the driver’s elbow and hand when gripping the handles, according to McGhee. This helps reduce arm pressure. Some seats are now molded to fit the contours of the body rather than exaggerating a flat board. "I know in the early years one of the huge complaints were the shoulder areas because your arms were always constantly out there forward, and I think adding armrests have helped," McGhee says.

Another new design that helps reduce vibration is a "rocker front end," that pivots separately from the frame and the operator, McGhee says. This allows the two front wheels to rock, reducing the amount of shock that is sent back through the operator.

"What that means is that if that one wheel is deflected a certain distance, it’s only going to deflect the center half of that distance," McGhee explains. "You’re not sending as much movement through the operator by reducing the amount of shock-loading movement that the operator sees due to potentially rough terrain," McGhee explains.

In addition to back problems caused by excess vibration, hands, and more specifically the fingers, are sometimes stressed when squeezing traditional pistol-grip drive levers. Mower manufacturers have redesigned the position of some controls to prevent hand and wrist problems such as carpal tunnel syndrome, but Waters says the disorder is not as widespread as back injuries. Only 2 percent of costs associated with occupational injuries nationwide are associated with carpal tunnel syndrome, he says.

Pistol grips have traditionally been designed like scissors in which the bottom lever moves away from the stationary handle, Busboom says. This does not allow the operator to evenly distribute pressure among all fingers. Some controls are now being positioned topside and inward, allowing the operator to use the entire hand, according to Busboom.

Also, on riding mowers, some handles are now placed in a more natural or neutral position that places less stress on the ligaments, Busboom adds.

Easy reach of controls keeps employees happy at Realiscape, Wake Forest, N.C., says company President Jim Barbee. "With the way they sit all day long, being able to reach for the controls comfortably is vital," Barbee says. "Having a bad back for years, I can tell you that’s very important."

Some mowers now have the parking brake incorporated into the steering handles as well to prevent excess bending, according to Ryan Crumly, design engineering manager, Auburn Consolidated Industries, Auburn, Neb. The brake is automatically set when the operator moves the handles to get off of the machine, Crumly says.

Overall, mid-mount zero-turn mowers are becoming more popular because the control efforts are extremely low, and visibility is increased, according to Lund. The mid-mount mowers put the operator in a better position relative to the edge of the deck, which reduces the number of blind spots, Lund says.

From an ergonomic perspective, improved visibility lessens the chances that the driver will have to make sudden twisting and turning movements to adjust controls. Also, more hydraulic, foot-operated and electric deck lifts are replacing hand-controlled deck lifts, according to Lund. "Instead of the hand-operated deck lifts where you had to bend at the waist and pull it back with your back, now you’ve got a little more ergonomic-friendly foot assist lift or electric or hydraulic lift assist," he explains.

FUTURE MOVEMENTS. While cost is a factor for most contractors, health usually comes first. "It doesn’t matter how much money you make if you hurt yourself," Barbee says. "You don’t want an employee to get hurt – you don’t want them to wear themselves out. You want to push for comfort and safety. I think that makes our employees happier, and that shows on the job, and I think our customers can sense that."

As far as future mower ergonomic standards are concerned, the topic is still relatively new in the industry. Advancements have been made mostly in response to customer feedback, Busboom says.

And most contractors are first interested in durability and speed, according to McGhee. Ergonomics is usually third in level of priorities. Last would likely be aesthetics, McGhee says.

"Ergonomics is a real concern," McGhee says. "It is something we look at a lot, but many times one of the things that keeps us from really pushing the envelope in machine design is cost. You can’t just throw things on there to throw them on there, and yet, you want to be able to produce a machine that people are going to be able to sit on for three or four hours at a time without having issues. We're doing things much better than we did five or six years ago, and most of that is market pressure."