Sports and other forms of recreation are neither traditional nor untraditional, in terms of seminary formation; they're entirely neutral. One may recreate in any legitimate way one elects to recreate, provided the seminary has no restrictions. For example, a seminary might decide that playing video games or watching television is verboten for a variety of reasons. But what would be objectionable about, say, soccer, or football, or hockey, or basketball, or any other competitive athletic sport?
As far as martial arts, well, you need to have a qualified instructor for that, and I would imagine most seminaries haven't got someone like that on staff. On the other hand, everyone knows how to play baseball.