Put a hand just below your ribs and let it move. Most of us breathe up in the chest, and the settling effect comes from lower down, where the diaphragm can actually shift.
You can check this lying down with a book on your stomach. If the book rises, the breath is going where you want it. If only your shoulders move, it is staying high and you will not feel much difference. Changing a habit this old takes a bit of practise, so give it a few days rather than a few breaths.
Qur’an and Sunnah
When I have fashioned him and breathed My spirit into him (Quran 15:29). Breath sits at the very beginning of what a person is, so it is no surprise that where it moves in the body makes a difference.
فَإِذَا سَوَّيۡتُهُۥ وَنَفَخۡتُ فِيهِ مِن رُّوحِي فَقَعُواْ لَهُۥ سَٰجِدِينَ
When I have fashioned him and breathed My spirit into him, bow down before him,’
Qur’an 15:29read it in the library
Translation: M.A.S. Abdel Haleem, The Qur'an, Oxford University Press, 2004.
What the research says
Slow abdominal breathing combined with biofeedback lowered blood pressure and raised heart rate variability in people with slightly raised blood pressure. Notice what was studied: breathing that was both slow and abdominal, in a group with one particular condition. That does not show chest breathing is useless, but it does put the low slow breath on firmer ground than the general advice to take a deep breath.
Wang SZ, Li S, Xu XY, Lin GP, Shao L, Zhao Y, Wang TH. (2010). Effect of slow abdominal breathing combined with biofeedback on blood pressure and heart rate variability in prehypertension.. Journal of alternative and complementary medicine (New York, N.Y.) doi
Strength of evidence: one line of research. A single study, or a theoretical account.
Why it works
The big muscle under your lungs is the one that presses on the nerves that slow you down, and it only moves if the breath goes low.
This one is still a draft. It is waiting on a scholar and a clinician to read it before it is published.
Near this one
To find the soft ocean sounding breath, breathe out through your mouth as if fogging up a mirror. Then keep that same slight narrowing at the throat with your mouth closed, and let the sound get quieter and quieter.
Any breathing instruction that reaches you through a screen or a book comes from someone who cannot see you. Keep the final say over what your body does.
The three ordinary breaths between rounds are not a gap in the practice. They are where you find out what the practice did.