Here is something that will put a spring in your step: a
backpack that bounces up and down on bungee cords instead of
pounding the shoulders and back. The bag's designer envisions
his creation as just what the doctor ordered to relieve the
spines of schoolchildren as well as military and emergency
personnel--all who risk injury from carrying heavy loads. When
people walk their hips move up and down by as much as seven
centimeters, which normally causes a backpack to bob up and
down, too. That is bad news for the joints and back, because on
its downswing the pack exerts added force on the wearer. A
50-pound load, for example, can slam down with 80 pounds of
force when a person is walking and up to 150 pounds when
running, says physiologist Lawrence Rome of the University of
Pennsylvania. The new backpack, crafted by Rome, is designed to
keep a load level with the ground during motion and, therefore,
counteract the jarring force of walking or running with a heavy
pack. In Rome's device, the load is suspended by