In the first study of its kind, Ohio State University researchers believe they have found an important factor in recurring back injury: our natural tendency to avoid using hurt muscles.
The findings point to new forms of physical therapy and new safety standards for physical labor in the workplace, which could affect the incidence of severe back injury and reduce costs associated with these injuries.
William Marras, professor of industrial, welding, and systems engineering, and his colleagues discovered that people tend to compensate for back injuries by using many inappropriate muscles in place of muscles that hurt.
"People with back pain guard the injured area by using more muscles than they need to," Marras said. "The more muscles they use, the greater the load there is on the spine."
Injured people may use muscles in their abdomen, sides, or other uninjured back muscles even though these muscles are not necessary for lifting. The study revealed that people with back injuries unknowingly inflict twice as much twisting force on their spine, and 1.5 times as much compressive force as uninjured people, when lifting the same object.
Across the United States in 1999, more than 420,000 people missed work because of back injury. Each lost an average of six days on the job, according to the U.S. Bureau of Labor Statistics.
The Ohio State study compared the lifting activity of 22 uninjured adults to that of 22 people who were suffering from lower back pain. No other studies have been able to make such a comparison because injured people are often unwilling or unable to perform the physical exertions necessary for these tests, Marras said. To solve this problem, the researchers created a mathematical technique to obtain needed information from the partial exertions an injured person can comfortably provide.
On average, the injured participants weighed more than their uninjured counterparts, and weight also increases force on the spine. That's why losing weight can help people recover from back injury, Marras said.
Another route to recovery, physical therapy, may have to change to prevent recurring back injuries, he added. Typical therapy for back injury involves helping the patient regain strength. But just as important as strength is learning to use back muscles appropriately.
The study suggests that this new rehabilitation strategy, combined with weight loss and a redesign of the workplace, could reduce the possibility of repeat back injuries.
The U.S. Occupational Health and Safety Administration maintains strict guidelines for preventing healthy people from becoming injured but not for preventing injured people from becoming injured again.
Marras said the guidelines for injured workers would have to be even more strict. "There are some motions, such as bending to lift far away from the body or lifting something off the floor, that a normal person can do once in a while without serious harm. Those are the kinds of motions an injured person should never do at all," Marras said. "Bottom line -- you can send people back to work after a back injury, but you have to be very careful about what you have them do."
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