Backpacks come in all sizes, colors, fabrics, and shapes and help kids of all ages express their own personal sense of style. And if they're used properly, they can be a useful tool for kids.

Many packs come with multiple compartments that help students stay organized while they tote their books and papers from home to school and back again. Compared to shoulder bags or purses, backpacks are better because the strongest muscles in the body - the back and the abdominal muscles - support the weight of the packs. When worn correctly, the weight is evenly distributed across the child's body, and shoulder and neck injuries are less common than if the child carried a briefcase or purse.

As practical as backpacks are, though, they can strain muscles and joints and may cause back pain if they're too heavy or are used incorrectly. However, there are steps you can take to help your child avoid back pain and other problems associated with improperly used packs.

What Problems Can Backpacks Pose?
Although many factors may lead to back pain - increased participation in sports or exercise, poor posture while sitting, and long periods of inactivity - some children have backaches because they're lugging around their entire locker's worth of books, school supplies, and assorted personal items all day long. But most doctors and physical therapists recommend that kids carry no more than 10% to 15% of their body weight in their packs.

To help understand how heavy backpacks can affect your child's body, it helps to understand how the back works. Your child's spine is made of 33 bones called vertebrae, and between the vertebrae are discs that act as natural shock absorbers. When a heavy weight, such as a backpack filled with books, is incorrectly placed on your child's shoulders, the weight's force can pull your child backward. To compensate, your child may bend forward at the hips or arch his or her back, which can cause your child's spine to compress unnaturally. Because of the heavy weight, your child might begin to develop shoulder, neck, and back pain.

Kids who wear their backpacks over just one shoulder - as many kids do, because they think it looks better - may end up leaning to one side to offset the extra weight. They might develop lower and upper back pain and strain their shoulders and neck. Improper backpack use can also lead to poor posture. Girls and younger children may be especially at risk for backpack-related injuries because they're smaller and may carry loads that are heavier in proportion to their body weight.

Also, backpacks with tight, narrow straps that dig into the shoulders can interfere with a child's circulation and nerves. These types of straps can contribute to tingling, numbness, and weakness in the child's arms and hands.

And bulky or heavy backpacks don't just cause back injuries. Here are some other safety issues to consider:

• People who carry large packs often aren't aware of how much space the packs take up and can hit others with their packs when turning around or moving through tight spaces, such as the aisles of the school bus.
• Students are often injured when they trip over large packs or the packs fall on them.
• Carrying a heavy pack changes the way a person walks and increases the risk of falling, particularly on stairs or other places where the backpack puts the student off balance.

Purchasing a Safe Pack
Despite their potential problems, backpacks are an excellent tool for children when used properly. But before you buy that trendy new backpack your kid or teen has been begging you for, consider the backpack's construction.

The American Academy of Pediatrics (AAP) recommends that parents look for the following when choosing the right backpack:

• a lightweight pack that doesn't add a lot of weight to your child's load (for example, even though leather packs look cool, they weigh more than traditional canvas backpacks)
• two wide, padded shoulder straps - straps that are too narrow can dig into shoulders
• a padded back, which not only provides increased comfort, but also protects your child from being poked by sharp edges on objects (pencils, rulers, notebooks, etc.) inside the pack
• a waist belt, which helps to distribute the weight more evenly across the body
• multiple compartments, which can also help distribute the weight more evenly

Although packs on wheels (which look like small, overhead luggage bags) may be good options for students who have to lug around really heavy loads, they may be less practical than traditional backpacks because they're extremely difficult to pull up stairs and to roll through snow. Check with your child's school before buying your child a rolling pack; many schools don't allow them because they can pose a tripping hazard in the hallways.