Schoolbags... a pain in the back?

I recall one particular concern I had when my eldest son started secondary school: the weight of his schoolbag. I reasoned that the weight of his bag must be harmful, particularly to an immature skeletal system, and that the consequences would inevitably be pain and potential damage to his spine.
It seems logical that a heavy bag must be potentially harmful. However, as I researched the literature in preparing this article, it became apparent that a heavy school bag and back pain don't automatically go hand in hand.
Whenever you research scientific literature you will find conflicting evidence - one article will show a relationship between two variables; another will show no relationship.
It is important when looking at scientific evidence that we are critical; we have to determine how well the study researches the question. I found some articles that suggested a relationship between heavy schoolbags and lower back pain, but I found just as many that suggested that carrying a heavy bag is not a significant cause of back pain in children and adolescents. That is not to say, however, that it is not a contributing factor.
When I looked more closely at the "better" designed studies, I found some common themes. Carrying a bag in excess of 10 per cent of body weight will not help someone who already has low back pain.
The adverse effects of carrying a heavy schoolbag appear to be more significant when the bag is carried for a long period of time - what is known as "sustained loading".
It is also generally agreed that carrying a backpack over only one shoulder is a potential cause of neck, shoulder or back pain.
Several studies also suggested that schoolbag weights may exceed the recommended guideline load limits for adult industrial workers, which is of concern.
What is more generally agreed in the scientific literature is that back pain in children and adolescents is multifactorial - there are often numerous factors which contribute to pain. In those children who have pain, carrying a heavy bag will contribute to the problem. Carrying a bag for long periods, and over one shoulder, may contribute to back pain. So will sitting for long periods, particularly with poor posture.
I know this information is probably confusing for parents. I believe there is no doubt that carrying a very heavy schoolbag is not ideal. I would love to see schools providing more lockers for children and for kids to use them.
I would also encourage children to use a well-designed school bag with wide shoulder straps, a waist strap, and compartments for loading. Children also need to carry the bag correctly.
Parents can play their part by providing a well-designed bag, encouraging their children to carry the bag correctly and lobbying schools to provide lockers.
Perhaps most importantly, parents can feel confident that carrying a heavy bag is not going to cause "damage" to a young spine.

Michelle Sintmaartensdyk is a physiotherapist at the Oamaru Physiotherapy Clinic. She has postgraduate qualifications in Manipulative Physiotherapy and Sports Medicine and is a Registered Physiotherapy Acupuncturist.