Heavy school backpacks aren’t just an academic burden for kids. New research finds significant numbers of teens carry packs topping 10-15 percent of their body weight that can cause back pain and other related disorders.

Researchers, writing in the Archives of Disease in Childhood, tracked back problems among 1,403 healthy students -- aged 12 and 17 years -- from nearly a dozen schools in Northwestern Spain.
The teens were weighed twice –once without the backpacks and other items they normally carried – and a second time, while wearing their packs.
Researchers found more than 60 percent of the teens carry packs that exceed 10 percent of their own body weight, while nearly 1 in 5 carried a pack topping 15 percent.
More than a quarter of the students told researchers they had chronic back pain – lasting more than two weeks -- during the previous year. Girls were more at risk of back problems than boys and they increased with age.
Those teens whose backpacks were heaviest were 50 percent more likely to have back pain for more than 15 days than those whose packs weighed the least.