The fact that we breathe alternately is very significant in swara yoga because it allows different swaras to flow at different times. One swara flows through the left nostril, another flows through the right, and the third flows through both nostrils together. The different swaras influence us in various ways by stimulating different energy centres and aspects of the nervous system.
In fact, it is not just by chance that the swara flows sometimes through the right nostril and at other times through the left. The rhythm of the body is based on the biorhythms, the energy rhythms of the body, and it also relates to the two hemispheres of the brain.
In the human body the three swaras correspond to the three major systems, which can be termed as a trinity.
Mind is one aspect, life force is another and spirit or soul is the (bird. Mind, life force and spirit combined constitute the human being. In swara yoga, mind is known as chitta, life force as prana and spirit as atma. Chitta controls the sensory nerves: the eyes, nose, tongue, ears and skin. Prana controls the five organs of action: speech, hands, feet, reproductive and urinary/excretory organs. Atma is the overall witness or controller.
When the left nostril flows, it indicates that the mental energy, chitta, is predominant, and the pranic energy is weak. When the right nostril flows, the pranic forces are stronger and the mental aspect is weak. When both nostrils operate together, it indicates that the spiritual energy, the
force of the atma, is in power.