When I tally up how many of my friends and relatives exercise at least occasionally, it comes out to less than ten. It's more like six. Not good. Exercise is one of those things that constantly gets put on the back burner. For most people, it ranks low on the priority list, behind laundry, cleaning, dining out, and spending time with friends. What's more, people are naturally inclined to expend the least energy possible. Exercise involves some effort, and for many people it's just easier to plop down on the coach and reach for the potato chips. I'm one of those who used to find any excuse in the book not to exercise: "I'm tired" "I'd rather stay home watching TV" "I don't want to get all sweaty" "It's too late to go today" "I can always exercise later" "I don't want to deal with traffic" "Going to the gym is boring" "I already ate" "I have too much t...