Hi,
I can offer a few considerations regarding this type of breathing. I have seen/used this type of breathing in other qigongs. I believe it is what you are referring to. Two inhales, and one exhale..
There are general ingredients to qigong that make it effective.
Oxygenation, infusing oxygen, heightening breath intake is one.
All gigongs work with breathing. I don't know of any who just focus on that particular breathing as an isolated thing, or something you can sort of put into another qigongs alignments/movements. In one context I know, it is 'part' of a walking qigong. The other parts are just as vital. Smiling, a sense of youthfulness, turning the head, stimulating the energy points on the feet. If I recall, probably a visualization of positive energy intake on the inhale and blockage release on the exhale. I would also add, that this qigong was practiced by cancer patients, and they would do this qigong, as much as six hrs a day. My sense is, that the smile, the visualization, the youthful vigorous manor, the bubbling spring point stimulation, etc etc, all are part of the deal. I would add, that we know the mind moves energy , so over emphasizing any physical piece/movement is not necessarily the way to disect and compose a better qigong for yourself.
I have also seen this breathing in martial qigong, again, to pack in oxygen.
Both other methods that I've seen a double inhale used, are not as ,,, I don't know how to say,,,,expansive?? quiet/empty/emptiness... They are more vigorous, very body focused. I don't equate that state to SFQ style qigong. The SFQ active exercises promote emptiness, as they are so expansive and quiet. In this more quiet state, I would add feeling state too, you can still focus on oxygen intake. A long expansive inhale, holding the upper breath a bit, still can infuse the lungs with plenty of oxygen. Awareness of really filling the lungs helps with this detail, if you like. Master Lin has also suggested exercise outside, relative to being by trees, perhaps pine?? for more oxygen(maybe someone else can clarify that). I find that, relative to oxygen, very helpful and useful. It gets you in relation to nature, not just within an exercise. I would add that air, is a basic element/elemental to engage with, communicate with, signals... what you breath in, the potential signals you can support in infusing and releasing/exhaling.
In straight forward medical qigong, the lungs are more or less completely filled to capacity, and completely emptied. A complete exchange of air. A sense of filling the lungs is good, and breathing out old stagnate air is good. Again, you can breath in SFQ, increase oxygen intake, tweek breathing to be very complete and vital, I believe, without the two inhales one exhale. I have nothing against that method, I use it in a martial qigong I still visit, but I don't see it as an ingredient missing in SFQ. As Shawn always mentions, there are more than one way to cook a potato.
In general, it is a mistake to put to much importance on a physical movement or breathing method. I consider emptiness a higher level to achieve, and the only methods I've seen utilizing this double intake of air are more vigorous physical gestures that don't really promote emptiness or feeling qi for that matter. There is good in that vigorous and oxygen intake, I'm not knocking it. My point is more that there is adequate breathing method in SFQ, and Master Lin has composed/composes a qigong relative to what he considers best. I don't consider him unaware of other qigong methods/specifics. You can't have every qigong technique out there in one qigong. Qigong systems have general qualities to their practices. Sometimes mixing in another method can mess with the general quality of the qigong.
For SFQ, again, I see it as a very soft, relaxing, expansive, opening up approach to the active exercise. Very feeling, and condusive to meditative or emptiness. Vigorous breathing, walking, gesturing, the pace of walking, are more a projected energy of sorts, or imposed physical gesture, versus feeling and openess, receptiveness. I'm just talking/thinking outloud. Just some things to throw in the conversation.
The visualization is how the mind moves the energy. That is key.
With that, you add in the smile, a sense of youthfulness. That is also key. I would say that reverse breathing is more the breathing method to focus on in SFQ, and within that, take deep elongated breaths, fill the lungs. You can heighten that oxygenation aspect, complete inhale, and still cultivate stillness or emptiness.
love,
gallen