MOWERS: The Ergonomic Advantage

To Webster, ergonomics means the applied science of equipment design intended to maximize productivity by reducing operator fatigue and discomfort in the workplace. To landscape contractors, ergonomics can mean more comfortable – and more productive – crews. But even as issues like workplace injuries and the rising cost of health insurance become more prominent in the landscape industry, manufacturers agree that ergonomics continue to take a backseat to factors like price and productivity. “Ergonomics are pretty far down on a contractor’s list of priorities,” says Bill Wright, president of Wright Manufacturing, Frederick, Md. “We hear thousands of comments about things like durability and functionality, but most contractors seem to be willing to tolerate some discomfort for the sake of making money.”
 
Despite the seeming lack of interest, advancements are being made to make mowers and other landscape equipment safer and more comfortable for those who operate them day in and day out. And while the advancements seem slight, like seats with more padding or handles with better grip, they could have dramatic affects on the industry, particularly from a productivity standpoint. According to the U.S. Bureau of Labor Statistics, in 2004, musculoskeletal disorders comprised nearly 32 percent of all nonfatal occupational injuries, with 27 percent of these injured workers missing 31 or more days of work. These injuries become more expensive to employers as each day goes by. “If a crewmember is absent even for a day or two, the owner or foreman has to account for that loss somewhere,” says Brian Roberts, director of ergonomic services, CNA Financial Corp., Chicago, Ill. “Quality and productivity are undoubtedly affected.”

WHERE IT HURTS. Soft tissue injuries, known as cumulative trauma, are the most common outcome of an ergonomically unfriendly workplace, Roberts says. With riding mowers, these injuries occur mostly in the lower back, but also in the ligaments and tendons of the shoulders and knees. With hand-held equipment and walk-behind mowers, the wrist is also susceptible to injury. These injuries are cumulative in nature and can lead to musculoskeletal disorders like sprains, strains, carpal tunnel syndrome and hernias.
 
There are a variety of movements that can lead to cumulative trauma, with two of the most common being improper bending and twisting of the lower back, Roberts says. “Bending, particularly to lift something, puts tremendous force on the lower back,” he explains. “Twisting on the way up is the worst motion you can make because you are putting more torque on the soft tissue in the vertebrae.”

Sitting on a stiff surface like the seat of a riding mower for hours at a time can also cause strain on the lower back, and the bumpy terrain of a lawn only makes it worse, Wright says. “We’ve noticed from our research that when a mower goes over a bump the front wheels dip down first followed by the back wheels, causing the seat to repeatedly bang against the operator’s back,” he explains. “To prevent that, the driver lurches forward and sits away from the back of the seat, leaving no support for his back.”
 
Contractors operating stand-on mowers should avoid standing rigidly with stiff legs, Wright says. A better method would be to mimic a skier, with a slight bend in the knee and a flexible back. “This way the body can flow with the bumps,” he says.
 
Another common motion that strains the lower back is lateral flexion, or carrying heavy items with the arms extended away from the body, Roberts says. “Extending the arms while lifting creates more force on the back,” he explains. “Keeping the elbows close to the side of the body gives the lifter the most strength and creates the least amount of force on the back.”
 
Hand-held equipment like string trimmers are known to cause cumulative trauma to the wrist, Wright says. Fortunately, these machines are usually used for no longer than 10 minutes at a time on most residential jobs. But on large commercial jobs, crewmembers may have to use them for anywhere from four to eight hours at a time depending on the size of the property. “The vibration of a string trimmer’s staff can numb an operator’s wrist after an hour, and the tingling can go all the way to the shoulder,” Wright says, adding that wearing a harness can help carry the bulk of the machine and alleviate some force.
 
Operating pistol grip walk-behind mowers can also cause stress to a contractor’s wrists. Because the squeezing action turns the mower on and off, it requires a good deal of force and has been connected to carpal tunnel syndrome Wright says, comparing the action to exercising too long with handgrips. “Contractors repeat this motion sometimes hundreds of times per day and their wrists can get very tired,” he says. “When using exercise handgrips, five squeezes are good, but after 20 you can’t squeeze anymore. That shows how much stress contractors can encounter throughout a typical day. Even with exercise you shouldn’t overdo it.”

BETTER ERGONOMICS. Improvements in design have helped make some mowers more ergonomically friendly. The largest leaps have been made in seat design, says Mark Woodlief, project manager, Husqvarna commercial wheeled goods, Charlotte, N.C. More, larger springs and suspensions absorb the jostles of a lawn’s bumpy terrain so the operator doesn’t have to. The backs of mower seats are also being made taller and more contoured to fit to a contractor’s body, preventing the back from twisting and turning, he says.
 
Wright agrees that today’s mower seats are receiving the most ergonomic attention, with some made with up to 6 inches of vertical spring stroke that can absorb even abrupt shock. “With a vertical 6-inch stroke, you can hit a groundhog hole and not really feel it,” he says. “With other mowers, that could knock your teeth out.”
 
The handles of some mower designs are being made at a seven-degree angle, the proper position in which a person would rest their hands while sitting down, Woodlief says.
 
Thick, textured padding on the handgrips of some mowers makes them easier and more comfortable to hold and also absorbs vibration. “Imagine holding a glass of tea,” Wright says. “You don’t want to drop it so you squeeze it very tightly. If the glass was textured, you wouldn’t have to exert as much force to hold on to it.”
 
Some manufacturers are going beyond just suspending the seat and are suspending the whole frame. This can make for a smoother ride particularly for contractors who mow for eight or more hours per day, Wright says. Mowers with suspended frames tend to have more moving parts than regular mowers, making them more expensive to purchase and maintain.
 
When purchasing a push mower, contractors should be sure to choose a self-propelled machine with an automatic start, Roberts says. This eliminates the need to push the mower physically and bend down to pull the mower on and off multiple times a day. If purchasing a stand-on mower, a padded sulky can help reduce some of the machine’s vibration, Roberts says. “How much vibration is absorbed will depend on the type of equipment, type of terrain and the ergonomic precautions,” he says. No matter what type, manufacturers suggest contractors purchase mowers with adjustable seats and handlebars to suit each rider. Some of today’s mowers can adjust to fit riders weighing 100 to 350 pounds, Wright says.  
 
Manufacturers agree that the costs of ergonomic additions are slight – less than 1 percent of the total cost of the machine, Woodlief says. An ergonomically friendly seat can cost $400 to $500, while foam handgrips can cost $10 to $20. Other upgrades like arm rests may add another $50 or $60. A more expensive upgrade, a suspended frame, may add another $1,000 to the mower’s cost. Wright says some manufacturers give their customers the option to mix-and-match their mowers so they can choose the ergonomic features that are right for their businesses.

EASE THE PAIN. Roberts says that many landscape crews get into ergonomically unfriendly routines that could be prevented with a reexamination of their daily practices. He suggests premeditating the layout of each job to keep necessary equipment and materials in the most accessible places. This will not only promote ergonomic consciousness, but also save time from a productivity standpoint. “I tell contractors to preplan their jobs in relation to the human interface,” Roberts says. “How far do crewmembers have to walk to get what they need? Is the plant material located on one side of the jobsite when it’s needed on the other? Were pallets unloaded from the truck just to be picked up and moved later? This type of consideration needs to be done everyday.”
 
Roberts suggests aiming for an additional half hour of productivity and a 10 percent reduction in the amount of walking, bending and reaching each day. “You’re reducing cumulative trauma and fatigue while increasing productivity,” he says. “There is no way to keep a crew 100 percent efficient all of the time. But that extra half hour a day will go straight to the bottom line and make a significant difference in the long run.”
 
Roberts says the price of an ergonomically unfriendly workplace can be broken down into direct and indirect costs. Direct costs include things like filing a claim, medical and insurance costs, and indirect costs include having to pay someone to cover the injured person’s responsibilities and lost productivity. Roberts says indirect costs can be four times more than direct costs. “If you have a $100 claim, the final cost to an employer will be around $400,” he says. “Someone may not be collecting those costs, but they are real and they are there.”
 
Just like it’s impossible to keep a crew 100 percent efficient all of the time, it’s impossible to eliminate 100 percent of the aches and pains. But to ease them, Wright says it’s a good idea to not spend too much time using any once piece of machinery. His suggested timeline is one-hour increments separated by five- to 10-minute breaks. An alternative is four-hour increments separated by 30-minute breaks. “This distributes the work to different parts of the body throughout the day,” he says.
 
There are exceptions, Wright says. For example, string trimmers should not be operated for more than one hour without a one-hour break. “It’s best for a body to stop repeating a specific motion for too long to avoid problems in the long term.”