自然呼吸(Freeing the Breath)。フツーに呼吸するという感じの表現ですが、 呼吸に関与する筋肉をストレッチしながら緩めていき、ゆっくりと深い呼吸をするということのようです。
【p30】
One of the best things you can do for your everyday well-being is learn to breathe with less effort and tension. Tension in the breath can reinforce pain and stress, but a relaxed breath sends a continuous message to your mind and body that you are safe and well. Releasing tension from your breath will let you breathe more deeply and smoothly with no extra effort.