Who's asking: Steven Dean, Mechanicsville, VA
Steve writes: "I was running with my shoelace untied the other day. As I watched my feet and shoelace, I started thinking that the mechanics of running (or walking) would seem to indicate that for a normal walk it would be impossible to actually trip on your own shoelace."
Steve, you're more coordinated than I am. I've done this more than once, so I can explain how this happens.
Left shoe's untied; left shoe's lace flops between the right and left feet. Right shoe steps down on the left lace. Left foot tries to step forward, but is restrained by the right foot, which is holding down the left foot's shoelace. Walker pitches forward, stumbles, lands on knees or face.
Don't try this at home, unless you're auditioning for "America's Funniest Home Videos." (Is that show still on?)
Anyway, this is one of several reasons I avoid shoes with laces. I didn't learn to tie my shoes until I was seven years old. I got reasonably good at knot-tying for sailing, 20 years later, but I'd still rather not have to tie my shoes.