Very interesting points have been mentioned by George Ledyard above. I have been training in aikido for some years now and have recently been training in some other martial arts (karate and judo). These have been "sport" forms of these martial arts and I have found it a very interesting experience. It is, of course, very hard to keep relaxed and centred in a competitive environment. It is a real eye opener and I hope my aikido will eventually improve because of it.