Back 2 School: How heavy is too heavy for backpacks?

(CNN/WBAY) - Students carry a lot on their shoulders--including a heavy backpack. Doctors would like parents to be mindful of the heft to prevent back pain.

Some doctors have treated children complaining of back pain linked to the weight of their backpacks.

Kids should carry no more than 20 percent of their body weight.

Place heavy textbooks in the back and lighter notebooks or supplies in the front.

Orthopedic Surgeon Dr. Nicholas Fletcher tells CNN that children should wear their backpack with both straps.

"In order to prevent it from falling and in order to prevent it from falling off, he's going to have to lean a lot to his left to hold that in place," says Fletcher. "So that's why it's important to have both straps."

Parents can help lighten the load by checking to see if kids are carrying more than they need.

"If you look here the bottom of the bag is right at the waist level, you don't want it sagging down and you don't want it too high up because it's going to pitch him forward a little more," says Fletcher. "But when you look at him from the side his head is nicely above his pelvis and waist."

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