Before sending your kids off to school, you may want to check the weight of their backpacks.

Previous research by a team of doctors at Childrens Hospital Los Angeles and the Keck School of Medicine of USC found that 37 percent of children reported back pain. Of those kids, 82 percent claimed their backpacks either caused their pain or made it worse, with 34 percent limiting their activity due to the pain.

The American Academy of Pediatrics recommends that backpacks never exceed 10 percent of the student’s body weight to avoid shoulder and back problems.

USC Health