TODAY | September 02, 2013
>>> a concern for parents and administrators as the new school year begins and it has to do with these guys. doctors expect to see a growing number of kids complaining of back pain. as tom costello explains, the culprit is pretty easy to spot.
>> reporter: back to school and back to the backpacks. coming in all shapes, sizes and color schemes but too often, too heavy, and too low. that pink backpack belongs to emily tate, a high school freshman near columbus ohio .
>> i don't have time to stop by my locker because it's out of the way so i have to carry everything in my backpack so it gets heavy.
>> 64% of 11 to 15-year-olds report back pain related to their backpacks and six months later 20% still have the pain. it can hold books, binders, a lunch, a phone, a coat and perhaps gym clothes. if it adds up to 30 pounds on a 100 pound kid, that's 30% of the child's body weight . way too heavy says the experts.
>> if it's too low, it will bring your spine backwards. if it's tie too high, too much pressure on your shoulders.
>> nicole mayer is an occupational therapist at nationwide children's hospital in columbus. ideally the backpack should weigh 10% of the child's body weight and should rest in the middle of the back. kids should wear the waist belt for added support and always wear both shoulder straps.
>> if they're wearing it on one shoulder it can pull the spine to one side and strain the muscles.
>> reporter: at ranch view middle school in colorado they're trying to take books out of backpacks. they now work off two sets of books.
>> we have classroom sets of textbooks where one set is in the classroom and one set is checked out and sent home with students.
>> parents need to watch for the warning signs. a sudden change posture or complaining of back pain. her bag weighs 14 pounds but she is petite.
>> smaller kids can only carry so much.
>> reporter: the bottom line, if it hurts, it's too heavy. for today, tom costello. nbc news washington.
>> how much is this one.
>> we put an anvil in this one to make the point.
>> this is ridiculous.
>> people load up these book bags .
>> i'm still lopsided from my backpack.
>> my back is like a question mark and if i don't correct it i'll sit like this.
>> so how much do you encourage or hope there's going to be an app for that? so that there are going to be kids that can use an ipad and actually study and have their books be apps.
>> they're doing this in colorado with the set of books at school and at home. that's a great idea although very expensive for school districts