White, Caucasian men tend to dominate strongman competitions.
Blacks tend to dominate boxing (I can only think of Tyson Fury and Klitschko) and sprint events.
Gymnastics is starting to have equal representation at the highest level.
MMA does tend to be predominately white.
A strange mix here.
I don't think it's about any sort of advantage. It's a cultural thing. For instance, the breeding grounds for MMA (the gyms) tend to be almost entirely White culture. From what I hear, this is even true in Asia. Boxing gyms tend toward Blacks and Latinos.