Neurons Spy on Breathing
Scientists at Stanford University studying breathing in mice found that a small group of neurons in the brain observe how the body is breathing. This cluster of neurons reportto another part of the brain, the locus coeruleus which "sends projections to practically every part of the brain and drives arousal: waking us from sleep, maintaining our alertness and, if excessive, triggering anxiety and distress."
This illustrates how breathing can deeply effect the psyche. If one is suddenly frightened, one of two things usually happens. Either a person's breathing freezes or it becomes rapid. If the breathing freezes the person's body will often freeze and if the breathing becomes rapid the person's body readies for fight or flight (sympathetic nervous system response). If similar breathing is done in a calm environment feelings of anxiety, fear and so on will often arise. Holotropic Breathwork and Rebirthing utilize such breathing to light up old traumatic pathways in the nervous system in order to integrate the material and clear it out of the psyche.
The breath can be seen as analogous to the use of a bellows for a fire. When one intentionally increases the rate of the pumping of the bellows the fire increases. As the fire increases it burns more fuel. The fuel is all of the suppressed and repressed material in the psyche. This sounds great in theory but it can be very rough in reality. Caution should be exercised when using forced breathing exercises. After doing the exercises one usually feels great but there is often a delay in time between the cause and the effect. Hours or even a day later one may have deep emotional material arise, deep depressions from nowhere, anxiety for no reason etc. The bellows have kicked up the dust and fuel that has been repressed or suppressed. I have read many teachers caution students about using certain breathing exercises but none explain this mechanism of delayed effect from the cause. A vicious circle can arise where the practitioner breathes forcefully making them feel better afterward and hours later has dark emotions arise...they then do the breathing again to feel better which kicks up more material from the depths of the psyche. This can lead to an overload and breakdown. Another odd thing to note is that in the day or so after doing such breathing situations in life may appear that bring up emotional material for the breather. I don't understand how this happens but I have noted this effect many times.
One may ask, "if this is true, why doesn't vigorous exercise do the same thing?" In my experience it is because the increased energy (the fire from the bellows) is used immediately by the strain on the physical body. When the energy is not used by the physical body it will be used by the psyche.
When the material comes up to be integrated it will feel terrible. When it feels terrible remember what Jung said: "“One does not become enlightened by imagining figures of light, but by making the darkness conscious.”