"There I am," a very fit patient is saying, "out on my five-mile run, motoring my way up a steep incline. Suddenly, I feel a throbbing pain in the middle of my right shin. Oh, no, I think, not again." As things turned out, the patient recovered from the shin splints1 quickly, but he knew he'd dodged

You're driving to work and stop for a red light. You're minding your own business and - bam! - your car rocks forward and backward, slammed in the rear by another car driven by some guy yakking on his cell phone. Or you're a passenger in a New York City taxi. The driver's cruising down Fifth Avenue when