
A bandha (Sanskrit: बंध) is a kriyā in Hatha Yoga, being a kind of internal mudra described as a "body lock," to lock prana into the body. Bandha literally means bond, fetter, or "catching hold of".
Mūla bandha is a primary bandha in traditional yoga.
Mula Bandha (Sanskrit: मूल बंध) is from Mūla, meaning variously root, base, beginning, foundation, origin or cause.
The earliest textual mention of mūla bandha is in the 12th century text Gorakṣaśataka, which defines it as a yogic technique to achieve mastery of breath and to awaken the goddess Kuṇḍalinī. It defines mūla bandha as:
[The yogi] forces the downward-moving apāna breath to move upwards by means of contraction. Yogis call this mūla bandha, "the root lock." When apāna has turned upwards and reached the orb of fire, then the flame, fanned by the wind, rises high. As a result, fire and apāna reach prāṇa, which is hot by nature. The overheated prāṇa creates a blaze in the body, which heats the sleeping Kuṇḍalinī and wakes her up. Like a snake struck by a stick, she hisses and straightens herself. As if entering a snake-hole, she enters the Brahmā naḍi. Therefore, yogis should maintain the regular practice of mūla bandha.
According to Tirumalai Krishnamacharya, this technique belongs to hatha yoga.
Iyengar defines Mūla Bandha as a posture where the region of the lower abdomen from the anus to the navel is contracted towards the spine and pulled up to the diaphragm. He likens the functionality of the Bandha and especially Mūla Bandha to "safety-valves which should be kept shut during the practice of kumbhakas". He specifies the energetic prāṇas of Vāyus engaged through Mūla Bandha as: "...Apāna Vāyu (the prāṇa in the lower abdomen), whose course is downwards, is made to flow up to unite with Prāna Vāyu, which has its seat within the region of the chest." He cautions that "Mūla Bandha should be attempted first in antara kumbhaka (retention after inhalation). He further states that "While practicing Mūla Bandha, the yogi attempts to reach the true source or mūla of creation."
Maehle defines it as "root lock" and further specifies that:
The root referred to here is the root of the spine, the pelvic floor or, more precisely, the centre of the pelvic floor, the perineum. The perineum is the muscular body between the anus and the genitals. By slightly contracting the pubo-coccygeal (PC) muscle, which goes from the pubic bone to the tail bone (coccyx), we create an energetic seal that locks prana into the body and so prevents it from leaking out at the base of the spine. Mula Bandha is said to move prana into the central channel, called sushumna, which is the subtle equivalent of the spine.
The action of mula bandha has been described as similar to a Kegel exercise.

Uḍḍīyana bandha (Sanskrit: उड्डीयन बन्ध), also called abdominal lock or upward lifting lock, is the abdominal bandha described and employed in hatha yoga, in particular in the nauli purification. It involves, after having exhaled all the air out, pulling the abdomen under the rib cage by taking a false inhale while holding the breath and then releasing the abdomen after a pause. The process is repeated many times before letting the air into the lungs, resuming normal breath.
Jalandhara bandha (Sanskrit: जालंधर बंध, IAST: Jālandhara bandha) is the chin bandha described and employed in Hatha Yoga and Ashtanga Yoga.
The name Jālandhara bandha comes from Sanskrit: जाल Jāla, web or net and (Sanskrit: धर) dhara, "holding".
This bandha is performed by extending the neck and elevating the sternum (breastbone) before dropping the head so that the chin may rest on the chest. Meanwhile, the tongue pushes up against the palate in the mouth.
Mahā Bandha ("the great lock") combines all the other three bandhas, namely:
In Ashtanga Yoga, these three Bandhas are considered to be one of the three key principles of yoga practice.
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