Gabe Sandvig is entering his junior year of high school in Fargo, North Dakota. He says his heavy backpack has led him to both the doctor and chiropractor in the past.

"I got tendinitis in my shoulder," he said, "from the tendons being stretched out and condensed so tightly."

He estimates his backpack on a typical day weighs more than 20 pounds, when full with all its contents.

"Typically, three notebooks, three textbooks, two reading books and four folders," he said.

Not to mention all the handouts that go into his folders. "They get pretty full," he said.

We put together a similar scenario to check the weight. It consisted of three large text books, a pencil case with some supplies, one notebook and one folder. It came out to about 13 pounds.

Our backpack didn't have everything Gabe described in his - but it's still heavier than a chiropractor would recommend for a 100-pound high schooler, like Gabe's sister, Hannah Sandvig. She's entering her freshman year.

"There's just so many classes," she said, "I feel like I'll probably have more text books and stuff like that."

The American Chiropractic Association recommends your child's backpack should weigh no more than 10% of her or his weight.

Amy Christianson, a chiropractor in Fargo, North Dakota, advises to not only take into account your child's backpack weight, but also its size. She says it shouldn't be longer or wider than a child's torso.

Christianson also advises children to use both shoulder straps when wearing the backpack, and if possible, also fasten any chest and waist belts for added support.