(WISH) – Another study for kids shows heavy backpacks could be causing problems.

Doctors said kids should not carry more than 10 percent of their body weight.

One parent said his kids bags tend to weigh anywhere from 10 to 30 pounds. That’s closer to 50 percent of the child’s weight.

“It puts a tremendous amount of stress, postural stress, gravitational stress on the neck, upper back, shoulders, muscles, joints, so it’s a pretty common problem,” Chiropractor, Dr. Dan Davidson said.RELATED: 15 things to put on your back-to-school shopping list

Davidson also said long term, the strain can cause posture problems for kids. They also said constantly staring down at electronic devices is causing a trend of back problems.CNN contributed to this report.