Among research available on the topic, "Influence of Carrying Book Bags on Gait Cycle and Posture of Youths," by David D. Pascoe et al., found that backpacks worn over one shoulder—the preferred fashion for many students—promote lateral spinal bending and shoulder elevation. This awkward posture also causes a change in gait, causing a reduction in stride length and an increase in stride frequency. This, in turn, puts more stress on the spine and muscles.
Some researchers have hypothesized that the greater number of steps taken with a backpack load may cause development of acute and chronic injuries due to the repeated mechanical stress associated with foot impact during walking, writes Pascoe, a professor and exercise physiologist at Auburn University. In fact, backpack-carrying students surveyed in the study complained of soreness (67.2%), back pain (50.8%), numbness (24.5%), and shoulder pain (14.7%).
Pascoe observes that as children get older, their homework and academic demands increase, which means they will likely increase their load of books and materials to and from school each year. "The potential for acute or long-term injury resulting from weight-bearing carriage using only one strap and bags without frames that do not distribute the weight to the hips may be considerable," he warns. "The ramifications of this weight-bearing induced stress, often applied asymmetrically, is a serious issue when considering children and youths who are experiencing physical growth and motor development."
Similar concerns for the development of young children were expressed in a 1988 report by the Hong Kong Society for Child Health and Development. After an examination of 812 students in the third through sixth grades, it was revealed that 5.54 percent had mild to serious spinal deformities. While the overwhelming majority of students in the study carried their backpacks over two shoulders, a majority of the children with spinal deformities carried theirs over one shoulder. Though the low number of students in this latter group fails to make the finding "statistically significant," researchers do point out that using only one shoulder is not recommended.
The Hong Kong study also found that most children's backpacks were twice as heavy as they should be. In recommendations based on this finding, researchers encourage parents to supervise their children when they pack their bags daily to make sure the load is not too heavy or unevenly distributed. They also encourage teachers, when possible, to allow students to complete their work in class so they will have fewer items to carry home.
Findings from a 1994 Scandinavian study indicate potential problems for kids no matter how they wear their backpacks. Researchers found that 53.7 percent of children who carried their bags over one shoulder complained of back pain, compared with 45 percent of those who carried their bags over two shoulders. Ironically, children experiencing the most pain were those who carried their backpacks by hand (68.6%). Further, results show females are more likely to experience back pain than males, and there was a significant increase in low-back pain found in the age group of 12 and over.
While the studies cited here each focus on different aspects of the issue, together they make a good case for caution—and prevention. ACA offers DCs and parents these tips on keeping young backs out of harm's way:
