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QUEST Volume 10, Number 2, MARCH/APRIL 2003

Power Assist: Add More 'Oomph to Your Push

Quickie Xtender provides help going up or down a hill.

by Christina Medvescek

Manual wheelchair users know their enemies: gravel, grass, sand, carpeting, uneven sidewalks, hills, ramps. Even the blessedly smooth concourse at the mall can be intimidating when youre at the end of your endurance.

And then there are the aches and pains of steady wheelchair use: shoulder degeneration, rotator cuff disease, repetitive strain injuries such as carpal tunnel syndrome, backaches, blisters, overheating and exhaustion.

Until recently, worn-out wheelers basically had two choices. 1. Ask someone to push them. 2. Switch to a powered device, such as a power wheelchair. The first option carries the implied frustration of relying on someone else; the second, the expense of a lift van and home modifications.

But technology is introducing a third option — the power assist. Just as the name implies, power-assist devices add a little "oomph" to your push, amplifying your strength up to three times that of normal, while still giving you the control, look and portability of a manual chair.

Frank Mobility's e.motion wheels fit most chairs.

Power assist is valuable for people who need a wheelchair for distances, but arent so weak that they need a power chair.

Power assist is "good for someone with a slower progressing neuromuscular disease who just needs a little help for longer distances, up ramps and over uneven terrain," says Jeanine Schierbecker, physical therapist at the MDA clinic at Washington University School of Medicine in St. Louis.

Whats It Do?

A combination of programmable software, a lightweight battery and motors in the wheel hubs, power assist adds turning power to the wheels whenever you push on the push rims. It stops when you stop pushing, and works in either forward or reverse directions.

In some models, wheelers can choose the level of assist required, from none at all up to 80 percent of the power required to move the chair. Other chairs come with a preset power-assist level, and some automatically shift levels when sensing the need.

Why Stick With a Manual?

Manual chairs offer physical, psychological and logistical benefits.

Surprisingly, the physical benefits probably are the least important. While it helps prevent atrophy, the exercise value of pushing a chair can be offset by the physical problems of overuse.

The pushing technique doesnt use a full range of motion and the activity doesnt appear to offer cardio-respiratory benefits. Other forms of exercise — swimming, hand cycling — are more valuable and less injurious, says Michael Boninger, executive director of the Center for Assistive Technology of the University of Pittsburgh Medical Center Health System.

Still, pushing a manual chair offers more exercise than using a power chair, Boninger says. "This [power assist] can help to prevent declines in strength associated with power chair use."

Psychologically, people who are "fighting the disease" often resist going to a power wheelchair, Schierbecker says, even though they may be working themselves to the point of exhaustion. In those cases, power assist can help them conserve their energy to keep pushing for a longer time.

But by far the biggest benefit is logistical — transporting a manual chair is far easier than carrying a power chair. A power-assist device adds from 37 to 53 pounds to a manual chair and doesnt impair its foldability.

In most models, the wheels can be easily popped off and stowed in the car trunk. If necessary, the chair can be hoisted up a couple of entry steps into a home, something thats impossible with a power chair.

The Downside: Cost

Still very new on the U.S. market, motorized power-assist units are selling for around $6,000. In some cases, that excludes the cost of the matching wheelchair, which can add another couple of thousand to the price.

Some models are covered by insurance and even by Medicare/Medicaid; others are still awaiting FDA approval.

Several models are available, each working somewhat differently and offering its own set of advantages and disadvantages.

Frank Mobilitys e.motion
(888) 426-8581

The e.motion is said to be the only battery-powered system that can be used on any existing manual wheelchair, instead of only on the manufacturers chairs. The system is self-contained within each wheel hub, and each wheel weighs 26.5 pounds, adding 53 pounds and up to 2 inches of width to the chair.

The wheels, which can be quickly installed without tools, offer preset power-assist options of 50 percent and 80 percent. Tapping a button mounted on the wheel mechanism shifts the power levels.

The battery range of about 8 miles is a bit short compared to that of power chairs; backup batteries are available. Costing $5,995 a pair, e.motion wheels may be eligible for Medicare/Medicaid funding under miscellaneous code K108, says the companys president, Werner Frank.

Quickie Xtender
(303) 218-4500
Quickie is a reliable name in wheelchairs, and its new power-assist device comes from technology developed by Yamaha, which has sold the device in Europe for several years.

The Xtender, which costs $6,295, only fits on the Quickie 2 or Quickie 2HP models, which cost an additional $1,945 (the Xtender price drops to $5,995 when you buy a chair, too).

The device comes preset at one of two power ratio settings: 1.5:1 or 3:1. A wheel synchronization system ensures that the chair rolls. Wheels are easilyremoved for transportation, and the whole system adds 37 pounds to the chair. The battery range is 9 miles.

The Xtender not only helps you go up a hill, but adds braking power coming back down as well.

(203) 230-0301
This system, which its manufacturer hopes will have FDA approval for marketing this year, takes yet another approach to power assist. A rigid wheelchair is combined with a motor, batteries, gearbox and software mounted under the chair, not in the wheels.

The system senses the difficulty of the terrain, then automatically provides as much assist as needed for the user to keep pushing at a consistent level of effort. DeltaGlide is expected to cost and weigh just a little less than the e.motion, and the wheelchair is included in the price.

Magic Wheels
(202) 282-0760
This product, scheduled to be released by the end of the year, is the least expensive version of power assist — a wheelchair wheel that adds pushing power through gearing (like a bicycle), not through a motor.

The two-speed wheels offer two power ratios — 1:1 (no help, no extra friction) and 2:1, providing 100 percent more hill-climbing force. Theyll fit on any wheelchair, including those that dont have quick-release wheels; will add only 7 to 10 pounds per chair, thanks to having no battery; and wont affect width or folding. Gears are shifted by a single hand on each wheel hub (precise finger control isnt necessary).

Developed with a grant from the National Institutes of Health, Magic Wheels are slated to cost less than $1,500 a pair. The system also provides automatic hill holding (with override) and automatic assisted dynamic downhill braking.

Improving Existing Chairs

You can gain a little easier push and lower your risk of injury by making some modifications to your existing manual chair, Boninger says.

If possible, adjust the rear axle position forward of your shoulder by several inches, he suggests. This allows for a longer, more efficient stroke. Vinyl-coated push rims also add a little power.

Make sure the chair is as narrow as possible, which helps keep your arms close to your body for a stable shoulder position. Have a physical or occupational therapist ensure that the height between your shoulder and the axle is proper for optimal power.

Being an overweight wheeler greatly increases the chances of developing carpal tunnel syndrome or shoulder-joint problems. Switching to an adjustable ultralight chair and having it professionally set up can help reduce the risk of developing arm pain.

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