Centro has a very light frame. He is actually pretty muscular through his shoulders and chest. If he was a TdF rider, his upper body would look like a famine victim.
Centro comes from a running family. A lot of kids built like Centro get passed over for sports because they are easily eclipsed by bigger kids who can kick a soccer ball harder, throw a longer pass and hit a baseball farther. The kids with heavier frames get all the good opportunities in sports in the US and the kids built like Centro are kept on the sidelines or just drop out of organized sports altogether. By the time you get to HS, the kids built like Centro have not been participating much in organized sports and are not in shape. So, the XC and track teams get populated with kids who were good at soccer (like Rupp) or basketball but not good enough to be on varsity. We really need to be looking out for kids built like Centro and make sure they have opportunities in organized sports if we want to have internationally competitive distance runners. In E. Africa, there is no issue because everyone has a light frame and everyone can go out and run.