Breathing seems to differ from one ma style to another. Boxers exhale hard through the nostrils to expel any blood. Tai Chi inhale and exhale as if smelling a rose. In Yoga some inhale through one nostril and out of the other one. With Karate inhale fast through the nose and slowly out the mouth. In TKD I would sometimes hold my breath while doing techniques. Bruce Lee would combine breathing with noises or strange sounds. How do you breath as a martial artist? Or how do you breath with in your chosen style?

For me you should breath in through nose and out through your mouth. This is from a combination of my University Training as an Exercise Scientist and my Karate Training.

This method is to prevent hyperventilation and an increase in blood pressure during techniques.

Holding your Breath during movements is not usually recommended due to the strain that it can place on your heart. This is actually called the valsava manoeuvre.