Research indicates that winning cyclists may indeed possess certain physical qualities that give them an advantage over the rest of the field. One of the most important of these qualities is excellent aerobic power. The greater the rate of oxygen delivered to the muscles, the greater the rate of work or speed that can be maintained. A study of racers in various categories reveals that racers in the higher categories generally have higher aerobic power. Clearly, aerobic power and racing performance are related.
Heredity plays a large part.
The idea isn't so startling when we consider the variation in other anatomical features. Maybe, but probably not. Fur one thing, the range of aerobic power among cyclists is very large. This certainly proves that aerobic power is not the sole determinant of success. And training makes a difference.