JACKSONVILLE, Fla. -- Kids are headed back to the classroom, ready to begin a new school year.

Some kids are a little more excited than others. Regardless, they'll have backpacks full of folders, crayons, pencils and pens. Wearing those backpacks could cause some problems in the future and it's important to wear them safely.

"Most backpacks come with two straps, and we definitely recommend that both straps are used. The straps should be snug but not uncomfortable. And the weight in the backpack should rest right around the lower back so the legs and the pelvis support most of it," says Dr. Kevin Neal, pediatric orthopedic surgeon with Nemours.

He also says the most important rule to follow, and the one that gets broken most often, is weight. Wearing a heavy backpack can cause not only short term, but long term back problems.

"Usually its called chronic or overuse type pain. Where from wearing too heavy of a backpack, the muscles and joints fatigue easy, and when they fatigue easy, they tend to spasm and hurt," says Dr. Neal.

Backpacks should not weigh more than 10% of a child's weight. If the child weighs 80 pounds, the backpack should weigh less than 8. Children should also put the heaviest things at the bottom of the bag, closest to their backs.