This is one of those myths of course. Yesterday I got a concerned "but how are your KNEES?" This would be the most common misinformed statement I have heard. Closely followed by one from an Aunt who was the first to tell me "I can't even run to catch the bus" when I told her I ran 3 miles twice a week. Then there was the obese "friend" not that long ago who declared "you will have a heart attack from all that exercise", strangely it was he who later had a heart attack, and he didn't even smoke. It is sad isn't it?