Dragon Ball Z. Instead of martial arts, there would be running.
The series would start with a rivalry between two teams - the turtle team and the crane team. The turtle team, despite having been a close rival for years, has been doing worse recently due to the departure of an older and more experienced competitor. They are saved from trouble by young Goku, a stray from nowhere (by the way, there were supposedly many such cases in Argentina and Brazil when you and I were children/young teenagers - children with talent "grew out" of the streets). It turns out that his genes and body are ideally suited to sports and running. I would solve the issue of enemies from space by having Freezer, Cell, Buu, etc. simply be competitors from other countries (like in Hetalia or Hajime no Ippo - Hawk was a symbol of how Americans treat the Japanese). They would have better coaches, better training conditions, take part in competitions more often, etc. The final battle with Buu would be some kind of mega marathon that takes place every few years.