Add this to the list of debunked widespread medical misconceptions: Children lugging heavy backpacks to school are no more likely to suffer back pain than those carrying lighter loads. If that's the case, another question emerges: If backpacks aren't the cause, why do so many children report lower back pain?
Dr Steven Kamper of the University of Sydney is concerned about the frequency of back pain in children. He told IFLScience: “Some children have back pain that comes and goes and doesn't upset them too much, whereas for others it persists and can stop them exercising or affect their mental health.” The problem, Kamper added, is that we don't know how to predict which category reports of pain will fall into, and therefore how to respond.
Moreover, Kamper explained, back pain in children has been understudied, unlike the same condition in adults. Therefore, we have little idea of the causes. Backpacks are the one exception. Often given as the explanation for children's muscular-skeletal pain – with guidelines advising against carrying a load weighing more than 10 percent of one's bodyweight for extended periods of time – they've been the subject of considerable research.
Kamper collected 69 studies, with a total sample size of 72,000 children, and published a meta-analysis in the British Journal of Sports Medicine. “Contrary to popular opinion, the findings are telling us that there is likely no link between back pain and schoolbag characteristics like weight, type and the way kids are carrying them,” Kamper said in a statement. The mixed designs of these studies (with some asking about pain while carrying packs, while most relied on reporting at other times) strengthen the robustness of the conclusions.
Given the intuitive sense that lugging a heavy load around for much of the day could contribute to pain, there's a question as to why the link isn't there. Kamper considers a “reasonable theory” to be that the regular use of a moderately heavy pack strengthens back muscles. The cases where children get ongoing damage from suddenly shifting to much heavier loads may be too rare to show up in the data.
Some of the studies Kamper used tested subjective estimates of packs' weight and did find a correlation with pain. Kamper thinks the most likely explanation is that children suffering from back pain for other reasons overestimate the weight of packs they have to carry.
All of which raises the question, what is causing the pain? “If you can tell me that, you'd solve a massive problem,” Kamper told IFLScience. Maybe with the most common explanation removed, we can start looking for other answers.