Some want to get in shape or to lose weight or to become more limber, or because they like martial arts or they like the philosophy of different styles. Their reasons don't really matter to us. My only objective is to prepare the student to defend himself on the street. That's the focus of our way of teaching. Gracie Jiu-Jitsu practitioners have extremely good breath control.
Breathing is also the result of practice and conditioning.
In training you learn to breathe. You train without losing the timing of your breathing. You accomplish this by remaining relaxed. But in order to be relaxed you have to have learned the basic elements. Then he can relax.