The American Chiropractic Association recommends that a backpack weigh no more than 5 percent to 10 percent of your child’s body weight. But studies show the average pack weight for middle schoolers is a hefty 15.6 pounds — well exceeding these guidelines.

All this weight can add up to recurrent lumbar (lower back) strain, poor posture and, in rare instances, future musculoskeletal problems. Dr. Mark Weston, an orthopedic surgeon specializing in spinal surgery, and Kory Bell, a physical therapist, offer these suggestions to help prevent back trouble.

Weigh in. Perch your child’s loaded bag on the bathroom scale. Does the bag weigh more than 10 percent of her body weight? Decide together what could be left home or in a school locker.

Appeal to style. To increase the “cool” factor of waist and shoulder straps, pitch in a few bucks so your children can purchase embroidered patches, pins, fabric paints or beads to decorate those key, back-sustaining straps.

Buy quality. The most back-friendly pack is on wheels. But if your child claims wheels are for old people, insist on a medium-sized pack with two padded, adjustable shoulder straps instead of one. This helps distribute weight evenly over a child’s back and shoulders. Waist straps, a padded back area and multiple compartments (instead of one huge holding place) also help minimize strain.

Pack smart. When a backpack sags to the buttocks, the back is more susceptible to injury. If your preteen refuses to cinch up shoulder straps, adjust the straps until they fit properly and hem or cut excess ends so they cannot be loosened. Also, teach your child to pack his bag with the heaviest items closest to the back and smaller or pointy items in outer pockets.