The countdown is on to the start of school.

There's only one week left of summer for kids in our area! The countdown is on to the start of school. Messenger Post's news partner, News10NBC catching up with our back to school family, the McCoys.

When it comes to backpacks, how heavy is too heavy?

"I have books in there that I bring home to study so my book bag might be a little bit heavy," Imani said. Her younger sister, Coco, says that's an understatement.

"A little heavy?! Your book bag is huge. Mine is about 10 or 15 pounds."

It turns out even that might be too heavy. Experts recommend a backpack weighs between five to twenty percent of your child's body weight.

Trelawney, Imani and Coco's mother, tries her best to keep the weight down.

"Sometimes I look at their backpacks and say, 'come here, what's in those bags?'" Trelawney said. "They may have shoes, gel, comb, brush, and all kinds of stuff in there."

Trelawney is on the right track. Dr. Joanne Wu, at Rochester Regional Health, said lugging around oversized bags have serious consequences.

"The growing spine does not tolerate a lot of mass on their back," Dr. Wu said. "It promotes chronic pain in the shoulders and joints as well as poor posture throughout the day."

Dr. Wu said parents should consider the safest bags when shopping.

"You want a bag where the straps are a little wider and have a padding to them," Dr. Wu said. "Also, as backpacks get to a high weight you can consider a hiking bag with straps across the chest and torso to evenly distribute the mass over the torso."

If children have frequent headaches, neck pain, or trouble concentrating, Dr. Wu says those might be signs the bag is too heavy.

She also says stay away from single-shoulder bags because they don't evenly distribute the weight.