Symmetric breathing is when the duration of the inhale, exhale (and possible retention) is the same. A popular example is “Box breathing or “Square breathing”. Inhaling (1,2), retaining (3,4) exhaling (5,6) retaining (7,8).
Asymmetric breathing are all other combinations, mainly when the duration of the inhaling and exhaling is different.
When we are in a state of mild activity our inhaling and exhaling duration is about the same. When we are excited or when we use our muscles intensively (like in “fight or flight”) the duration of inhaling gets longer than the duration of the exhaling.
When we are very relaxed, no danger or threats (like “rest and digest”) the duration of the exhaling is longer that the duration of the inhaling.
Breathing exercises that stimulate are asymmetric breathing, where the duration of the inhale, is longer than the duration of the exhale.
Breathing exercises that calm us are asymmetric breathing where the duration of the exhale, is longer than the duration of the inhale.
Our body interprets longer exhaling duration compared to inhaling duration, as a signal that there is no danger around. We can use asymmetric breathing to calm down and relax. It is individual and the best way to go about it, is to experiment.
The rhythm that I found to be very relaxing for me is 2_4. Inhaling using 2 stage breathing, abdomen 1 and then lungs 1 (in total inhaling 2), no retention…. And then exhaling through the nose. Lungs 2 then abdomen 2 (in total exhaling 4).
4 _ 7_ 8
One popular example of asymmetric breathing is 4_7_ 8. After fully exhaling, we inhale from the nose to the count of 4, retaining the breath to the count of 7 and exhaling from the nose to the count of 8.
In this practice the “bottle neck” is holding the breath to the count of 7. After repeating the sequence a few times, some people may feel breath shortage.