GETTING "PUSHBACK" FROM A WHEELCHAIR.

• Position: YOUR LIFE

When you push someone in a wheelchair, you may be hurting your back without knowing it, according to a study in Ergonomics. Researchers measured the forces on the spine caused by pushing a wheelchair, and discovered that people are not good at judging when they are exerting forces strong enough to hurt their back.

When asked to push a simulated wheelchair against increasing resistance, study participants typically exceeded the recommended limits to avoid back injury by nearly 20% before they decided to quit.

There is no specific ergonomic standard when it comes to pushing wheelchairs, explains integrated systems engineer William Marras.

Caregivers can judge only whether they can push a patient based on how their back feels and, with rising obesity, patients are getting heavier and harder to push.

"Today, patient handling is one of the most-dangerous jobs for your back. It's more dangerous than working in construction, more dangerous than mining or any of the other jobs we typically think of as difficult," says Marras, citing data from the Bureau of Labor Statistics.

Along with obesity rates in the U.S., the...