You send your kids out the door, lunch in hand, backpack loaded. Wait, what is all in that backpack? Have you picked it up lately to feel how heavy it is? If not, you should. Your kids might be lugging around much more weight than you think and it can affect their health.

A backpack that is too heavy can place stress on muscles and soft tissues, which in turn causes fatigue and strain. This can further lead to an increased risk of neck, shoulder, and back injuries and even nerve damage.

Children can hurt themselves by using poor postures, which can include arching the back, bending forward, twisting, or leaning to one side—while lifting or carrying a heavy backpack. Such postures can negatively affect the spine’s alignment so its disks cannot absorb shocks as they should.

Here are some tips from experts for parents and children:

1. Pick a lightweight backpack with two wide, padded shoulder straps, a padded back, and a waist strap, which can help spread the load.
2. Use both straps to spread the weight and promote good posture. Using one strap means one side of the body bears most of the weight.
3. Take care when putting on and taking off backpacks. Avoid twisting too much. When bending to pick up a heavy backpack, bend with both knees, not at the waist.
4. Position the backpack evenly in the middle of the back, near the body’s center of gravity. The backpack should sit 2 inches above the waist.
5. Adjust the shoulder straps so the backpack so you can easily put it on or off. The straps should allow you to move your arms freely, without being too loose.
6. The backpack should weigh at most between 10 and 20 percent of the child’s body weight.
7. Load the heaviest items closest to the child’s back. Use all the compartments to spread the weight.
8. Make frequent school locker stops to remove items that aren’t needed right away.
9. Remember that rolling backpacks must be carried up stairs.

Always keep in mind how heavy your child’s backpack is and make sure it fits them properly. Meet with your primary care provider for more information about your children’s health and the type of weight they are carrying on their back.