April is backpack safety month. This is mostly directed toward school-age children, but does also apply to anyone who carries a backpack.

To carry a backpack incorrectly over time is not unlike having a poorly designed work space, or lifting with the low back as opposed to the legs; it can be a precursor to injury.

Many career soldiers with jobs that require carrying a "rucksack" retire with back and leg problems related to this. In the case of a developing child or adolescent it can get them off to a bad postural start. The old adage "as the twig is bent, so grows the tree" may be valid in this context.

The orthopedic journal Spine stated that by their teen years 50 percent of youths will experience at least one episode of low back pain. Yes, half of kids report having back pain. It is thought that improper use of backpacks may make a significant contribution to this figure. The Consumer Safety Commission estimates that there are about 5,000 emergency room visits annually due to injuries related to backpacks and book bags.

When a backpack is carried, abnormal stresses and strains are imposed on the spine. There are some simple steps that can be taken to mitigate a backpack's effect on a growing (or even mature) spine.

First, the pack needs to be sized appropriately for the child's body. An adult version will have too widely spaced straps and be too long to fit the child's torso.

Second, a pack should never be worn with only one of the straps. Both shoulder straps and the waist strap (provided there is one) should be used at all times. Next, the pack's load should be distributed evenly using any pockets to even the load. Finally, the pack should not exceed 15 percent of the carrier's weight. This means if your child weighs 100 pounds, the pack should not exceed 15 pounds. Often children carry packs weighing 25 percent or more of their weight. Imagine a 200-pound man carrying a 50-pound pack all day.

Weigh your child's pack (and your own). and you may be surprised at what you find. Observe how an overloaded backpack distorts posture. Most notably it will cause the wearer's head to jut forward in camel-like fashion, which can lead to permanent postural distortions and spine injury.

April is national backpack safety month. Make safety a habit. Check your children's packs, before they complain of pain. It is an investment in the future health of you and your loved ones.

Dr. Nick Smith is a chiropractor at Active Life Chiropractic Center in Helena and is Montana's only certified Biomechanics of Posture practitioner. Reach him at 443-3965 or www.activelifemt.com.