The Associated Press

Some children are literally bogged down with heavy loads of homework.

Carrying the books and other tools to do their assignments from school to home and then back again is a source of potential injury, according to Dr. Avrom Gart, medical director at the Cedars-Sinai Institute for Spinal Disorders in Los Angeles, since many kids carry backpacks that weigh more than 50 percent of their body weight.

"Over time, children carrying this kind of weight can develop serious back pain and other problems that require treatment," he says.

Compared to a tote, satchel or briefcase-style bag, backpacks are typically better for children because they distribute weight evenly across the body but there are still problems with children arching their backs or leaning forward, affecting their posture, Gart explains.

Also, children who wear the backpack on only one shoulder and lean to one side to compensate for the extra weight are candidates for a condition called scapular winging, a pinched nerve that affects the shoulder muscle.

Gart recommends the following steps to help children wear backpacks safely:

• Weigh each item normally kept in the backpack separately so that children can determine which items should be carried versus what can be left at home or in their locker or desk at school. Children should not wear more than 15 percent of their body weight.

• See to it that children are only carrying necessary items; the bag should be cleaned out daily.

• Encourage children to use both straps.

• Watch children to see if they are slouched or leaning to one side, or if children are experiencing back pain, tingling or numbness in the shoulders or arms.

• Teach children to pick up backpacks by bending at the knees and grasping them with both hands. before putting it on.