“A child wearing a backpack incorrectly or that is too heavy can be contributing risk factors for discomfort, fatigue, muscle soreness, and musculoskeletal pain especially in the lower back,” says Karen Jacobs, EdD, OTR/L, CPE, clinical professor of occupational therapy at Boston University.

Understanding how the back works can help you see things a little more clearly. The spine is made of 33 bones called vertebrae, and between the vertebrae are discs that act as natural shock absorbers.

When a heavy backpack filled with books is incorrectly placed on the shoulders, the weight's force can pull a child backward. To compensate, a child may bend forward at the hips or arch the back, which can cause the spine to compress unnaturally. The heavy weight might cause some kids to develop shoulder, neck, and back pain.

Selecting a proper backpack and preventing back pain is simple. Follow these guidelines from the AOTA:

• Always select a backpack that is the correct size for your child.
• Make sure the height of the backpack extends from approximately 2 inches below the shoulder blades to waist level, or slightly above the waist.
• Always wear well-padded shoulder straps on both shoulders so the weight is evenly balanced.
• Distribute weight evenly. Load heaviest items closest to the child’s back and balance materials so the child can easily stand up straight.
• Wear the hip belt if the backpack has one, to improve balance and take some strain off sensitive neck and shoulder muscles.
• Check that the child’s backpack weighs no more than 10% of his or her body weight. If it weighs more, determine what supplies can stay at home or at school each day to lessen the load.
• If the backpack is still too heavy for the child, consider a book bag on wheels.