The Dept of Health and Human Services ran an article on HHS.gov about backpacks.This is what they want you to know about children and adults using backpacks.

Backpacks are a better option than shoulder or messenger bags for carrying books and supplies because the weight of the pack is evenly distributed across your body. However, backpacks that are overloaded or not used properly can make for health problems.

How Can Backpacks Cause Problems?

People who carry heavy backpacks sometimes lean forward. Over time, this can cause the shoulders to become rounded and the upper back to become curved. Because of the heavy weight, there’s a chance of developing shoulder, neck, and back pain.

If you wear your backpack over just one shoulder, or carry your books in a messenger bag, you may end up leaning to one side to offset the extra weight. You might develop lower and upper back pain and strain your shoulders and neck.

Not using a backpack properly can lead to poor posture.

Carrying a heavy pack increases the risk of falling, particularly on stairs or other places where the backpack puts the wearer off balance.

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 also are injured when they trip over large packs or the packs fall on them.

How Do You Know If a Backpack Is a Problem?

You may need to put less in your pack or carry it differently if:

• you have to struggle to get your backpack on or off
• you have to lean forward to carry your pack
• you have back pain

If you adjust the weight or the way you carry your pack but still have back pain or numbness or weakness in your arms or legs, talk to your doctor.

Tips for Choosing and Using Backpacks

• Consider the construction. Before you grab that new bag off the rack, make sure it’s got two padded straps that go over your shoulders. The wider the straps, the better. A backpack with a metal frame like the ones hikers use may give you more support (although many lockers aren’t big enough to hold this kind of pack).
• Carry it well. Before you load your backpack, adjust the straps so the pack sits close to your back. If the pack bumps against your lower back or your butt when you walk, the straps are probably too long. Always pack your backpack with the heaviest items closest to your back. Don’t drop all your stuff in the main compartment (using the side pockets will distribute the weight more evenly).
• Try a pack with wheels. Lots of kids use these as an alternative to backpacks, but there are guidelines and considerations to keep in mind with this kind of pack, too. Many schools don’t allow rolling packs because people can trip over them in the halls.
• Limit your load. Doctors and physical therapists recommend that people carry no more than 10% to 15% of their body weight in their packs. This means that if you weigh 120 pounds, your backpack should weigh no more than 12 to 18 pounds. Choosing a lightweight backpack can get you off to a good start. Use your bathroom scale to weigh your backpack and get an idea of what the proper weight for you feels like.
• Pick it up properly. As with any heavy weight, you should bend at the knees when lifting a backpack to your shoulders.