What Makes Michael Phelps So Good?

Some have suggested that Michael Phelps' Olympic success is due in significant part to his anatomy - that a long wingspan and unusual flexibility in his ankles give him that extra edge over the competition. 

But as Scientific American reports in an interview with a sports medicine physician, Phelps is not "freakishly" outside the norm in any bodily measure.  While it is true that being tall (basketball), petite (gymnastics), or having 20/12 vision (baseball), confers an advantage, it is more often hard work and training that differentiates the very good from the very best.