By Gillian Tsoi

Heavy schoolbags are damaging the backs of many children, according to a new study.

One in four teenagers, who regularly carry schoolbags that weigh 10-15% of their body weight, are at risk of back pain and other related disorders, researchers found.

These disorders include scoliosis and curvature of the spine. These back problems are compounded by a predominantly sedentary lifestyle.

Researchers in Spain assessed the back health of 1,403 pupils from 11 schools between the ages of 12 and 17.

The teens were weighed with and without the rucksack they normally carry to school.

Their height was also measured and information was obtained from their teachers about their lifestyle, sporting activities at school, sedentary activities at home and underlying health problems.

Information on back health was also sought, including a diagnosis of a spine disorder and the presence of back pain.

Most (92%) of the teens used a rucksack with two straps, which weighed almost 7kg on average.

Well over half of the teens (61.5%) were carrying rucksacks that exceeded 10% of their own body weight, while almost one in five (18%) carried a rucksack that topped 15% of their body weight.

A quarter of the students (just under 26%) said that they had had back pain for more than 15 days during the previous year.

The most common back problem (70% of those with a diagnosis) was scoliosis or curvature of the spine, followed by lower back pain, and contractures - continuous and involuntary muscle contraction.

Girls were more at risk of back problems than boys and their risk seemed to increase with age.

Previous research has linked rucksacks to altered gait and posture, which can result in chronic pain and other back problems in the long-term.

The researchers said that many children carry excessively loaded backpacks, which is harmful to a developing body.

They have urged doctors and teachers to start advising parents and children on the risks of carrying heavy bags to school every day.

The study was carried out at the University of Santiago de Compostela in Spain and published online in the journal Archives of Disease in Childhood.