But before sending them out the door this school year, parents should first check their backpacks to see if they're too heavy.

Dr. Jeannine Baer with The Association of New Jersey Chiropractors says it is important to make sure a backpack has two adjustable, padded shoulder straps and multiple compartments to keep the contents in place.

She said a child wants to have a lot of different places to put things. Heavier books and items should be placed toward the bottom and back of the backpack.

Also be sure that sharp, pointy objects such as pencils, protractors and compasses are not poking into a child's back or shoulders.

When is a backpack considered too heavy? Baer said to follow the red, yellow, green system. The green zone means if a backpack weighs less than 10% of a child's total body weight, then a parent does not have to do anything.

If it's in the yellow or the cautionary zone, that means the bag weighs between 10% and 15% of total body weight.

"It's not bad but it's sort of a warning to say this is starting to get heavy. We really want to make sure the fit is checked. We want to make sure they are not carrying extra things in there that are adding to the weight," said Baer. That could include water bottles or library books that are not needed on a daily basis.

If the backpack is in the red zone, which would be greater than 15% of total body weight, that's an alert.

"That's a stop-right-there. Check that backpack immediately," she warned.

Remove anything that is not needed. Maybe pull out some books that a child can carry in their arms instead.

Baer, who also has a private practice in Stirling, suggested that parents first weigh their child, then weigh the backpack. Divide the weight of the backpack by the weight of the child and that's how a parent will get the red, yellow or green number.

Heavy backpacks can lead to backaches and pain, shoulder pain, muscle tightness and postural changes. If not treated, these backpack injuries can last into adulthood.

Check the backpack routinely every month.

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