I resemble several of the stories posted here. My hand-eye and large muscle physical coordination has always been lousy, and I missed most of the normal child development milestones, such as crawling and walking, by many months. My early elementary school teachers became very concerned about me because I could not sort how to skip or to jump rope. I did learn to play piano pretty well and to type pretty fast and accurately, so at least some of my motor wiring seemed to work.
I became a chubby, low-activity preteen who could excel on the chess board or in academic classes, but I was always the last one picked on any sports team. Since I was not good at sports, I developed no interest in them. What completely changed my life was finally being able to balance a bicycle at age 12 (don't laugh). To my parents' complete surprise and delight, I asked them to buy an old Schwinn 2-speed middleweight from one of my classmates, and I began to ride to friends' houses, to nearby stores, or just out for fun. I had finally found MY sport. Six months later I requested and received a low-end Bianchi road bike for Christmas, and I started getting into mechanical work.
By the time I started at University, I was a fairly dedicated recreational and transportation cyclist, and I was well on the way to reconfiguring my physique. The two physical high points of my life came the year I turned 22. I completed a 12:18 double century, and the father of one of my boyhood friends came into the bike shop where I worked and finally figured out who I was, after not recognizing me at all -- "oh ... you were that little ROUND kid."
Bicycling is still my favorite sport, although I do enjoy walking, jogging, and hiking, as well, and I lift weights to preserve what little upper body strength and bulk I have. Bicycling has also literally saved my life, because I am certain I would be diabetic or a heart attack victim by now if I had kept up my inactive childhood lifestyle.