By age 18, it might be impossible to fix any damage to the spine

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Though laptops and tablets have helped lighten the load in students’ backpacks, many kids are still carrying way too much. And the effects are starting to show.

“I see quite a lot of spinal changes,” Dr. Arkady Lipnitsky of Pain Physicians NY tells PEOPLE. “We see kids walking around half-bent with these huge backpacks. That by itself completely changes the way the postural muscles are working.”

The current recommendation is that children and teens carry no more than 10 percent of their body weight on their backs. “But who are we kidding? Most of these backpacks are 20 or 25 lbs.,” Dr. Lipnitsky says. “That puts many kids closer to 25 percent of their body weight, which definitely has an effect on the spine.”

One major problem, Dr. Lipnitsky says, is that many kids don’t complain of or even feel any pain as a result of carrying too much weight. “Their parents might bring them in because they are concerned about their shoulders being uneven, or their posture being off,” he explains. “But many kids don’t feel pain because the changes associated with carrying too much weight are gradual.”

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Parents should look for changes in their kids’ spines, or posture, or the way they’re walking. If they notice a change, a doctor can do a posture analysis or a functional movement analysis to see how the child can stand, jump, squat, run or walk — “see how the body reacts in motion,” as Dr. Lipnitsky explains.

If there is a noticeable issue, it can generally be treated by exercise, though some cases might require a brace or “more drastic changes.” However, by age 16, it gets hard to repair the damage, and by age 18 it’s “nearly impossible,” Dr. Lipnitsky says. “When we stop growing, everything is fused and we can no longer make that adaptive change.”

Key to combatting these symptoms is a solid backpack. Though rolling backpacks have become more popular in recent years, “if kids are up and down on the bus, the staircase, that creates its own problem with lifting, as most kids don’t know how to lift properly, they just pull,” Dr. Lipnitsky says.

A “good” backpack should have two well-padded shoulder straps (a chest belt is a bonus) and hang above the waist. And kids should do what they can to leave heavy books in their lockers or at home when possible, though, as Dr. Lipnitsky says, “kids always manage to find something else — sports gear, coats — to carry. But schools also need to make spaces for kids to stash their athletic clothes and extra books.”