Heavy backpacks can cause long-term harm to children's shoulders and spines. Studies show that 10-30% of children experience back pain by their teenage years, which may be linked to carrying heavy backpacks daily. One study found that the average backpack load was 22% of a child's body weight, and over 30% of children carried loads over 30% of their body weight at least once a week. Carrying heavy backpacks can cause children to adopt a forward head posture. Reducing backpack loads to 10% of a child's body weight or less can help maintain normal posture and lung function.