Elite sports are very selective, those at the top have a the genetics and the commitment. Track cycling, which is very explosive, will favour athletes with a lot of fast twitch fibers, e.g. muscular build. Take a look at good look at cyclists at the other end of the spectrum: climbers. There's is just no elite climber that has a track cyclist build and vice versa.
And the climbers are endurance athletes, so they tend to be stringy or have that skinny fat look that endurance athletes have. Large muscles have no place, track cyclists need explosive speed=larger muscle, fast twitch muscle...
If you look at the Greyhound vs The Spanish Galgo, you'd see a very similar build, except the greyhound's muscles are rounder and fuller, and have more fast twitch fibers, the Galgo's muscles are flatter, and it has less fast twitch fibers...the Galgo is used to course hares and rabbits over a longer period, so it needs endurance over outright speed...
