The analysis of the breath is the anatomy of prana — its flow in the nadi system and its relationship to breathing. Pranayama, in turn, is the science of manipulating the flow of prana. It consists of an extensive set of breathing exercises.
We encounter the term prana in several contexts, and in each context the meaning is somewhat different. Some yogic scriptures instruct you to draw the prana in through the right nostril and expel it through the left. Here, prana simply refers to breath. We also come across passages that advise us to draw the prana into the elusive sushumna, the central channel. Here, prana means “the subtle life force”; this is the word’s most common meaning.
The term prana is inextricably linked to pranayama. Pranayama leads to an even distribution of prana between the two aspects of the nadi system. This in turn leads to freedom from the extremes of the mind and the removal of many of the obstacles on the path of yoga. The balancing of the nadis also prepares for the third and most important effect of pranayama, the suspending of the mind.
The blocking of the central energy channel in the Muladhara (base) chakra causes the life force to be diverted into the two adjacent channels, which are the solar (pingala) channel, relating to the right nostril, and the lunar (ida) channel, relating to the left nostril. The oscillation of life force between ida and pingala and the analogous oscillation of breath between left and right nostrils drives the oscillation of the mind between the extremes of relativism on one hand and fundamentalism on the other.
Pranayama practice restores the balance between the extremes of the mind and thus keeps the mind from oscillating between its extremes; more important, pranayama draws prana back into the central channel. Pranayama, then, is the training that utilizes the power source of the mind (prana) to return the mind to its original purpose and function.