Reading up on David Sime, the white American guy who lost the 100 meter dash gold medal by an inch or two at the 1960 Olympics in Rome, I noticed that he grew up a Chip Hilton-style football-basketball-baseball star in high school without running track. In college at Duke, the track coach noticed his “lanky build” on the baseball field and asked him to try sprinting in his spare time. He instantly turned out to be one of the fastest sprinters in the world.
What’s characteristic of that era when white men were highly competitive in sprinting and in running and receiving the football is that Duke’s track coach assumed that lankiness equates with sprint speed.
It makes sense that carrying around less upper body muscularity would help you accelerate faster. It was widely perceived in American sports at the time that there was a distinct negative correlation between speed and elusiveness versus strength and robustness.
Holding athletic training constant, a wide waist is bad for sprinting. As I mentioned in the NH thread “Grappling is for TTs”, strong white men tend to have very large waists (better for wrestling) as opposed to strong blacks, who tend to have very broad shoulders (better for boxing). Strong white men also tend to be heavier per volume due to more dense musculature, probably a diminished relic of neanderthal hyperplasia.
I think it is important to keep in mind that the lore of somatotypes is garnered mostly from common sense observations from the late 19th-century translated into the rigor of early 20th-century social sciences. An artifact of this is a heavy racial bias: black people simply were not represented. When Sheldon published The Varieties of Temperament in 1942, his thesis held that white bodies fall along three axes that correlate with their behavioral counterparts: endomorphism, ectomorphism, and mesomorphism (although he called them visceratonia, cerebrotonia, and somatotonia, respectively).
While we find that blacks and Asians can also be muscular, fat, or skinny, these are not necessarily the same as white somatotypes. As in the elementary example above, muscular blacks tend to be better sprinters than skinny blacks, because they both have skinny waists (and at least partly because skinny blacks tend to have worse diets). Poor white males tend to be fat, while poor black males tend to be skinny, despite similar diets. Poor Asians in America, though few at present, seem to be following the white pattern. Hispanics follow the black pattern.
And then there’s polymath :-P.