The term bandha is related to the English word “bonding.” We bond breath, movement, and awareness together. The bandhas are a means of controlling and directing pranic energy in the body. They are essential to the advanced practice of yoga. Without them, the energy produced by the practice cannot be properly utilized.
All bandhas involve muscular contractions but this is only one aspect of them, and the ancient yoga texts list bandhas among the most important yoga techniques.
Practiced with pranayama or in isolation, the bandhas work with the organs and the nervous and endocrine systems. They can help to ease disorders of the reproductive and urinary systems, sexual dysfunction, back problems, and recovery after childbirth.
You can think of the bandhas like the one-way valves in your circulatory system. These valves allow blood to flow in one direction as the heart pumps but not to reverse its flow on the upstroke, ensuring proper direction of blood flow. The bandhas direct the life force in similar way.
Yoga practitioners learn to tone certain sets of muscles in order to provide a lock, or closure, that holds psychosomatic energy and moves it powerfully through the subtle energy channels. This generates a physic heat in the subtle body that helps to simulate the awakening of the kundalini energy.
There are three primary bandhas in the body - Mula Bandha, Uddiyana Bandha and Jalandhara Bandha. Each bandha is a lock, meaning a closing off of part of the interior body. These locks are used in various pranayama and asana practices to tone, cleanse and energize the interior body and organs.