I have to say that I really got lucky and Im afraid I cant give you any tips because I sort of found my specialty by chance.
Like you I enjoyed working out and martial arts during the end of my highschool, so thats all I did. When it came down to choosing my major in college I logically chose sports sciences. I actually hated the stuff they taught us, the only part I enjoyed was sports medicine, so thats how I decided to start going to med school. So I moved to another country and learned a new language because in my home I couldnt have gotten into med school.
After one year of medicine I knew that I wanted to do molecular biology and biochemistry. I told my parents I would switch majors again. They werent very enthusiastic at first but now they know, as did I from the start, that this was a good choice.
So Im a few years behind my peers, but because of the fact that I really enjoy what I do I am also alot better than them. I really love what I study and I dont regret any decisions I have made, nothing else could make me this happy for the rest of my life.
The only tip I can give you is to just do what you think you want to do and not give a damn about anything else. I feel sorry for those people that go study business just because they think they will make alot of money. Maybe you will make lots of money, but you couldnt pay me enough to have me do work that I dont like for the rest of my life.