May 21, 2003 ANN ARBOR, Mich. – Backpacks have gotten a bad rap. For years, specialists have urged school children to lighten their loads, wear their backpacks on both shoulders and avoid lugging around those heavy school bags whenever possible. But new research from a University of Michigan Health System physiatrist indicates backpacks don't cause the stress and strain on young backs that they've been linked to.
"There is no good scientific evidence to support the claim that schoolbag load is a contributing factor to the development of low back pain in growing children," says Andrew Haig, M.D., medical director of the U-M Spine Program and associate professor of Physical Medicine and Rehabilitation and of Surgery at the U-M Medical School. Rather, he points to signs that children's activity level and weight may have more to do with back pain.
Despite a flurry of attention to this issue, Haig's study is the first to actually measure pain related to backpack use.
The study, which will be presented Wednesday, May 21, at the World Congress of the International Society for Physical and Rehabilitation Medicine in Prague, Czech Republic, looked at 184 elementary and middle school children in the Ann Arbor, Mich., public school district. The study focused on third grade pupils and middle school students; ages ranged from 7 to 15.
The children were initially asked about their backpack use, back pain, activity level and transportation to school. Haig and his colleagues then examined the pupils one day toward the end of the school year, before their first class. The children and their backpacks were weighed, and the child's height was measured. The numbers were used to determine the backpack weight as a percentage of body weight.
Virtually all the students said they used a backpack every day. Third graders were found to carry 5.7 percent of their body weight while middle schoolers carried 11.4 percent of their body weight. Also, despite warnings against carrying backpacks on one shoulder, most children did not sling their backpack straps over both arms.
With this kind of normal usage, the study found no link to back pain.
More than one-third of the children said they had at least one indicator of back pain. But the students who did indicate pain in their neck, middle back or low back did not carry heavier backpacks than those children who had no back pain. Further, the study found no relationship between back pain and whether the children wore their backpacks on one or both shoulders.
Good news for fashion-conscious students: "You can be cool again with your backpack over one shoulder," Haig says.
Since public attention turned to the potential for backpacks to cause pain in young children or teenagers, schools have fought back by restricting backpack use during school hours and looking for ways to reduce backpack loads. California lawmakers required schools to buy two sets of books – one for use in the classroom, another for use at home – so students were not carrying books back and forth. Samsonite even sells a specially designed backpack meant to minimize strain on the back.
Because students in the study primarily carried their bags to and from school, the time spent with heavy books slung over the shoulder is minimal. It's even less for children who ride the bus to school, which the majority of the children in this study did. The middle school students involved in the study did not carry their backpacks between classes.
"The spine may be able to handle heavy loads for short intervals without detriment," Haig says. "The children only wore their backpacks from school to home, which may not be enough time for damage to the spine to occur. The length of time a backpack is worn likely has an impact on whether a person develops pain."
Haig acknowledges that the study was done near the end of the school year, when homework assignments – and therefore backpack loads – may be lighter. Some of the children also reported that they had already turned in some textbooks.
Even if backpacks are not causing pain, the researchers were surprised by how many children reported some kind of trouble with their spine. The middle school children were more likely to report back pain than the younger children, 45 percent vs. 15 percent. Possible explanations for this increase with age can be found in the activity levels of the children.
"The students' body mass index, an indicator of obesity, increased from the third graders to middle schoolers, so the middle schoolers were more fat. Also the percent of students who walked or biked to school dropped dramatically in the older kids, so they're much less active. At the same time, they reported watching much more TV and spending more time playing video games," Haig says. "Frankly, I think that might be more of a factor in back pain than the backpacks."
Exercise squeezes and stretches the disks that act as shock absorbers for the spine. This motion pumps nutrition and oxygen, keeping the disks healthy. When people don't get that movement, it can starve the disks of nutrition and may be a cause of pain.
"We acknowledge the intuitive sense of parents, clinicians and teachers that as children carry more in their backpacks, they have more back pain," Haig says. "But the increases in pain seem to be related to aging and inactivity. Possibly, for children who have back pain, wearing a backpack can make that ongoing pain more uncomfortable. But there is no evidence that backpacks cause anything more than temporary discomfort."
### Visit the U-M Spine Program at http://www.med.umich.edu/pmr/spine/.
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