Math. Took very little time. No papers. Never once saw any of my teammates on campus as the math building was off in a corner. Most athletes took boutique majors at my school: Afro Studies, Sociology, Recreation, etc.
Got NSF grants for epidemiology, statistics, and economics.
Got an economics Ph.D. and wondered if I shouldn't have done episode or statistics.
I wish I had spent a lot less time running and more time getting to know the geniuses in my department (top research University).