Wednesday, May 02, 2007

"Lift with your legs" -- but how should you push?

The ergonomics of pushing ...

"A back injury can destroy a person's life. The pain can be so excruciating that even "passive" activities like sitting up to read a book become intolerable. Whether you work in a steel mill or sit at a desk, a back injury can make it impossible for you to earn a living. Even worse, for many of those who suffer with chronic back injury, is that because it's difficult for others to see what's wrong, there's a tendency to not believe the problem is "real."

Yet there have also been significant efforts to prevent back injuries. For decades, it has been known that lifting heavy objects is an important cause of back injuries -- nearly everyone knows that you should "lift with your legs, not your back." Workplaces have been modified to reduce the amount of lifting workers must do, replacing lifting tasks with pushing or pulling when possible.

But pushing and pulling tasks can also cause back injury -- accounting for 20 percent of all workplace back injuries in the U.S., U.K., and Canada. Fifty percent of all industrial materials handling jobs involve pushing and pulling.

Granata and Bradford Bennet recognized that while much is known about the stresses placed on the back by lifting, little research has been done on the problem of pushing and pulling.

The work that has been done hasn't taken the cocontraction of muscles into account -- the use of opposing muscle groups to stabilize the area of the body doing the work. They developed a mechanical model of pushing that incorporated cocontraction. Then they asked eleven volunteers to push against a special handle that measured the amount of force they applied. Goniometers measured muscle activity on the key areas of their back:"    (Continued via Cognitive Daily)    [Ergonomics Resources]

Ergonomics of Pushing - Ergonomics

Ergonomics of Pushing

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