Discomfort was most common in the shoulders, lower back, upper middle back and neck.

The findings may point to an emerging trend between pain and discomfort and time spent carrying backpacks, suggested study co-author Dr. Karen Jacobs, a former president of the American Occupational Therapy Association (AOTA) and a board-certified professional ergonomist.

"Most students -- in fact, 84 percent of the study participants -- are aware of the potential consequences of incorrect backpack usage," Jacobs said in an AOTA news release. "There is a pressing need to better educate students on how to prevent discomfort, which is the purpose of National School Backpack Awareness Day," which takes place on Wednesday, Sept. 17, and involves special events to educate students on the proper way to wear a backpack and how much weight to carry.

A loaded backpack should weigh no more than 10 percent to 15 percent of a student's body weight. For example, a student who weighs 100 pounds should carry no more than 15 pounds of weight in a backpack.

Jacobs offered a few suggestions on how to reduce weight.

"Carry water bottles empty and fill them before class. Carry only what you need and leave the rest in your room," she said.

More information

The American Academy of Orthopaedic Surgeons has more about backpack safety .