Description: Even ardent runners wonder if all that pounding won't eventually harm our knees, hips, or back.

My 85-year-old Aunt Marian thinks it's pretty cool that I'm a runner. Only problem: She wants me to give it up. The way she sees things, I'm doing fine now, but trouble looms. A few years down the road, I'll probably need a wheelchair. All that pounding and wear and tear; it can't do a body any good. Marian's got her share of aches and pains, and loving auntie that she is, she doesn't want me to end up in even worse shape.

I bet you've got an Aunt Marian in your life, too--a family member, or friend, or coworker who's always tsk-tsking the toll running is taking on your knees, hips, and back. You might even be worried yourself. We all know a few onetime runners forced to become swimmers, cyclists, or mall walkers. We wonder: Does the same fate await us?

The logic behind the wear-and-tear scenario can seem convincing. After all, your car eventually breaks down, even if it's a Volvo. Same