MONDAY, Dec. 5, 2005 (HealthDay News) -- Backpacks carried to and from school by the average American child are too heavy for safety and need to be reduced, warns a new report.
The University of California, San Diego-led study included five girls and five boys, aged 13, who wore identical backpacks fitted with pressure sensors in the shoulder straps. The children first carried 10 percent of their body weight in the packs, then 20 percent, and finally 30 percent of their body weight.
With each increase in weight, the children reported increased shoulder pain levels. Surface pressure was higher than the pressure threshold (30mmHg) that obstructs normal skin and muscle blood flow.
As reported in the Dec. 5 issue of the Archives of Pediatric and Adolescent Medicine, the study found that when the children's backpacks were loaded with 20 percent of their body weight, pressures measured 70 mmHg on the left shoulder and 110 mmHg on the right shoulder, more than double and triple the threshold for reduced blood flow.
Previous research showed that children commonly carry backpack loads of 22 percent of their bodyweight.
Strap pressure was much higher on the right side than on the left side at all weight levels, which may have been due to posture. This requires further study, the researchers said.
"The concern of heavy backpacks and back and shoulder pain to parents is not new. However, the objective data that we have published is new and important. The more objective data the public has, the more educated they become, and perhaps more inclined to change the way children carry backpacks," co-principal investigator Gita Murthy said in a prepared statement.
"Furthermore, manufacturers and designers of backpacks often try to optimize design based upon the data available in the literature. Our shoulder loading data may help designers and engineers design a wide shoulder strap, for example, that will help spread the load of the backpack," Murthy said.
The American Academy of Orthopaedic Surgeons has more about backpack safety.