COLUMBUS, Ohio -- People who lift heavy
objects are equally likely to injure their backs whether they wear a supportive
back belt or not, according to a new study at Ohio State University.
This study suggests that belts do little to prevent back injury, even though many companies in the moving, construction and material handling industries mandate that workers wear them.
Subjects in the study, which appeared in a recent issue of the journal Clinical Biomechanics, wore three types of back belts -- elastic, leather and orthotic -- while lifting heavy objects. Orthotic belts maintain the curve of the spine.
Only the elastic belt lightened the load on subjects' backs, and then by only 10 percent. The other two belts had no effect.
The lead author of the study, William Marras, professor of industrial welding and systems engineering and physical medicine and rehabilitation at Ohio State, said that elastic belts were likely to prove even less helpful in everyday life.
"We found that elastic back belts offered some protection
when people firmly planted their feet on the ground before lifting," said Marras. "But in real work situations, most people don't plant their feet; they shuffle their feet and move around. So if back belts offer any help at all under realistic circumstances, it's a very small effect."
Marras said that belts do not offer a quick-fix solution to back injuries on the job. "For example, you can lift about 20 percent more weight when you wear a back belt, but that doesn't mean that you have 20 percent more protection on your spine. So you may try to lift more than you can handle and hurt yourself."
Marras also pointed to other studies that revealed the negative effects of back belts. Under-utilized back muscles may atrophy when people wear a belt for a long time, so that they are more likely to injure themselves while lifting if they ever stop wearing a belt. Normal use of a back belt also raises blood pressure.
"If you already have a back injury, and you wear a belt, it helps you recover a little bit faster," said Marras. "But if you've never had a back problem, there doesn't seem to be much of evidence that it does any good, and there seems to be a whole lot of evidence that it does some harm."
Since most previous studies in this area focused on the recuperative aid of back belts to injured patients, Marras and his colleagues decided to study the effects of different types of back belts on 15 uninjured, healthy young men, mostly graduate students at Ohio State.
The researchers employed a device Marras invented called a lumbar motion monitor (LMM), a lightweight replica of the spine that straps on to a person's back and electronically monitors movements in three dimensions.
Each subject wore the LMM combined with an electromyograph that measured muscle activity while they lifted heavy boxes. The researchers then used these measurements to determine the loads that pressed down on each subject's spine as they lifted the boxes.
The researchers took measurements as the subjects lifted boxes that lay in front of them and off to the side, some at ground level and others high up -- typical box-moving motions in industry. The subjects lifted the same loads with and without each type of belt.
The elastic belt proved helpful only when the subjects turned to lift boxes off to the side. So that researchers could measure the force on the spine, each subject had to plant their feet and turn only with their upper body.
"We think the elastic belts helped simply because they are wide," said Marras. "They connect your pelvis and your rib cage, so you have to turn your trunk as a unit, without twisting your back. If you can independently move your back and your pelvis, then you twist your spine, which means you work your muscles harder and put more force on your spine when you lift something."
Right now, each industry decides independently whether its workers should wear belts. For some jobs it's up to the worker, while for others belts are mandatory.
"I advocate a third strategy," said Marras. "If you've had a back injury, and a back belt is prescribed by an occupational physician, then I think it's OK to wear it. My warning to people is, 'balance the positive effect of back belts with the possible negative effects that are out there.'"
Contact: William Marras, (614) 292-6670; Marras.email@example.com
Written by Pam Frost, (614) 292-9475; Frost.firstname.lastname@example.org
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