A bicycle is a time machine because it slows down time and aging. When I was a kid I rode everywhere and to school. Mid life I didnt ride much, but when my oldest boys got old enough to ride in the mid 80s I took up riding with them, and have been riding ever since. I will be 77 this year, and am very fit. I ride about 30 miles every other day. While genes have something to do with it, I credit biking for keeping me in good shape.