The Kanji "Bu" means "to stop the spear". This must be understood as the search of non-opposition, this is the reason why Master Funakoshi insisted on passing from "Jutsu" to "Do", acting naturally, not going against nature and adapting to its laws, favoring man's evolution. In Budo, technically, you change the "attack" with "non-attack".
In sport you are taught to obtain victory. In Budo you must teach the concept of "losing", which does by no means mean you must let yourself be hit, it's a matter of learning a way of transcending victory or defeat, going beyond selfishness, the only way to become "one" with the opponent.
In Japan there is a saying "to lose is to win". In Budo when you receive a blow, you must be grateful, because it teaches a lesson.
In competition there is a need of establishing rules and prohibit many dangerous attacks, just as military exercises rules are imposed in a certain space, forgetting that in actual war there are no rules; you are attacked from all sides. Many rules are established but in a real confrontation, those things that are prohibited are those most important & I practice what the rules do not permit.
In competition you only concentrate on your front side, if you concentrate on your back it's a waste of time. In Boxing you fight in a very upright position because blows directed to your lower section are prohibited. In competition, just as in Boxing, because low blows are not permitted, the guard goes up, this due to the fact that you are sure nothing will happen. In Budo, where the concept is integral, the guard (kamae) changes....
If we observe sports Judo, we see that combat begins by grabbing, without pondering the possibility of an attack before that point in time, there is no study of ma-ai (distance and timing). In Kendo, in the past, the training position was kokutsu-dachi. In our days, due to sports rules, the guard has risen and there are no longer gedan level attacks. In the past blows were delivered obliquely from the neck, with the intention of going through the body. Today you only attack the head with sharp blows and without using the hips.
With respect to tsuki, the intention was to hit and penetrate in large body areas, due to the fact that it is very hard to hit small areas. Considering the difficulty in protecting your legs, many joint attacks were studied. Today those techniques are prohibited precisely because they are very hard to guard against attacks.
In any normal sport the judge only assures himself that rules are followed and has no power to decide who wins, something that does not occur in sports karate where the judge can decide who has won.
You can see that there are many differences between real combat and sport and this is visible in kamae (not only the physical guard but also the attitude). Kamae expresses itself in a way that denotes the mental state and attitude (level of ki), and even though sports competition blows may hurt, their goal is not to kill the opponent. Actually, analyzing competition in terms of real combat, it is better to receive the blow and afterwards strike with the idea of going through the physical barrier. Under those circumstances, do not be afraid, let yourself be hit and enter with decision.
From competition to the real form everything changes.