Being as boards like these have a large weeaboo percentage, you might want to try out kyudo. (Yeah, kyujutsu was already mentioned, but generally kyudo is more readily available.) Look it up on Wikipedia for details, but in a nutshell it's like traditional japanese archery in a ritualized, formal sort of way. The improvement aspect is there, though you'll mostly be tinkering with yourself.

Also, what >>7 said about the martial arts.