Injuries that take place in childhood can have long-lasting effects—and as kids return to school this fall, they may be packing a future of back pain along with their books.

An overstuffed backpack puts children at risk of injury, according to Joshua Hyman, M.D., director of orthopedic surgery at New York-Presbyterian/Morgan Stanley Children’s Hospital.

“Parents should inspect their child’s backpack from time to time. They often carry much more than they should with extra shoes, toys, electronic devices and other unnecessary items,” said Hyman, in a hospital press release.

“A backpack shouldn’t weigh more than 15 percent of the child’s weight, or about seven pounds for a child who weighs 50 pounds,” he added. “If it is textbooks that are making the bag too heavy, parents should speak with the teacher—sometimes these books can be left at school.”

To prevent injury, children should also wear a backpack correctly over both shoulders to spread the weight evenly. Alternatively, they should consider a wheeled backpack.

If the child experiences persistent pain, parents should consult with their pediatrician, who may recommend physical therapy to strengthen the back muscles. Some indicators of trouble include when the child’s posture changes while wearing the backpack, when they struggle to put it on, or any pain, tingling or red marks.

Related articles:

World Backpack Day Promotes Kids’ Health