Last week's column urged that we make it more inviting for children to walk or ride their bikes to school, weather permitting. The idea is twofold: encourage more physical activity for kids and reduce the high traffic volume that is typical at most schools.
But I didn't mention one deterrent that can halt the walk-or-ride plan same as a morning downpour or subzero wind-chill readings. Several readers made the point for me.
"I am not fond of my kids riding their bikes to school because of how big and heavy their backpacks are," wrote one mother. "I think a heavy backpack could cause a child to lose their balance on a bike."
Another mom, Diane Cassidy, e-mailed her concerns, then talked in detail by phone.
"A heavy backpack causes you to walk with your trunk too far forward," said Cassidy, a physical therapy assistant and mother of three. "It puts too much pressure on the discs in the spinal cord."
Cassidy said physical therapists are well aware of the dangers of carrying too heavy a load for too long. She discussed Wolff's Law, which roughly translates to "bone molds to pressure."
"If you visit a botanical garden, you might see a tree tied down so it will only grow in one direction," said Cassidy. "Carrying too much weight on your shoulders can distort your shape."
Cassidy said her teenage son complains of back pain and occasionally lies down to relieve muscle tightness. "His backpack is ridiculously huge."
There is considerable debate about whether overloaded backpacks directly cause back pain and injuries in young people. A recent study at the University of Michigan Spine Program determined that a child's activity level and body weight are stronger predictors of back troubles. Yet the Consumer Product Safety Commission reports that more than 21,000 backpack-related injuries were treated at hospital emergency rooms, doctors' offices and clinics in 2002. But most experts agree that students should carry no more than 15 percent of body weight in their backpacks. Adults can maybe handle up to 20 percent of body weight.
Another mother e-mailed to note her high school daughter's science textbook was "5 pounds" itself. More is out of alignment here than children's spines from too often carrying a pack on only one shoulder (a bad idea).
Some state legislatures are taking matters into hand. California has passed a law requiring the state board of education to limit textbook weight by 2004. A committee is still hammering out the tenuous notion of judging a book by its poundage.
Tennessee passed similar legislation. At least seven other states have proposed backpack bills.
There are other solutions. Cassidy's son attends a daily study hall at York High School in Elmhurst, Ill. The extra period frequently helps the teen avoid bringing home one or two books more each night.
Another possibility is students' keeping two textbooks, one at school and one at home. This option is likely cost-prohibitive for most school districts. In response, one Massachusetts middle school parent-teacher organization raised $6,000 to buy two sets of books for every student.
Rolling backpacks represent another idea, but these bags on wheels can create stress on the shoulder from twisting around to pull the load. Plus, some administrators joke that their schoolyards resemble an airport terminal.
One theory among physical therapists and orthopedic specialists is that people who carry overloaded backpacks are overscheduled and, in their minds, overworked. A quick fix is switching to a lighter bag, which forces the issue of what can be lugged around. Kids have less choice if they intend to get good grades.
For mom Joey Harmon, that means exercise comes in other forms.
"Where raising healthy kids really starts is with an active family and active parents," said Harmon, whose high school freshman daughter rides a bike to school on days when her book load is light. "If my kids can't ride or walk to school, I'm happy to know they get their physical activity in other places."
(Bob Condor writes for the Chicago Tribune. Write to him at: the Chicago Tribune, 435 N. Michigan Ave., Chicago, Ill. 60611.)
(c) 2003, Chicago Tribune. Distributed by Knight Ridder/Tribune News Service.