Rhythm pervades the universe. The swing of the planets around the sun; the rise and fall of the sea; the beating of the heart; the ebb and flow of the tide; all follow rhythmic laws. The rays of the sun reach us; the rain descends upon us, in obedience to the same law. All growth is but an exhibition of this law. All motion is a manifestation of the law of rhythm.
The effect of rhythmic motion will give you an idea of the effect on the body of rhythmic breathing. The whole system catches the vibration and becomes in harmony with the will, which causes the rhythmic motion of the lungs, and while in such complete harmony will respond readily to orders from the will.