Mula-bandha

Mula-bandha

मूल, mūla — the root; बन्ध, bandha — lock

Root lock, lock of muladhara.

The concentration of energy at the point between the anus and genitals for its transformation and subsequent direction into sushumna, accompanied by physical impact on perineum by muscle contraction or heel pressure.

3.14. Press the heel of the left foot to the perineum, compress the anus, then press the navel carefully toward the spine (drawing in the belly).
3.15. The right heel rest on the genitals. This mudra destroys aging is called mula-bandha.
3.16. He who wishes to cross the ocean of being, must perform this mudra secretly and in a secluded place.
3.17. The practice of this mudra will undoubtedly lead to achieving perfection in mastering the breath. So practice carefully, in silence and without interruption.

"Gheranda-samhita"

Compression of the anal sphincter and heel pressing are mentioned in many classical texts, but in fact are not necessary. It is enough just to strain the perineum itself – this is mainly recommended by practitioners. However, the heel option may be convenient when performing maha-mudra or maha-bandhas that involved mula-bandha in itself.

Mula-bandha is connected with apana: helps to control apana and redirect its downward movement; participates in the awakening of sushumna and Kundalini Shakti. In the texts you can find a detailed description of this process:

36. Mula-bandha: apana, which tends to descend, is directed upwards by the force of sphincter of the anus. This process is called mula-bandha.
37. When apana rises and reaches the area of agni (fire), the flame of the agni becomes long, as it is inflated by the vayu.
38. Then, in a heated state, agni and apana mix with prana. This agni is very hot. The fire that arises in the body awakens kundalini with its heat.
39. Then the kundalini makes a hissing sound. She straightens like a snake, which is struck with a stick, and enters through hole of brahma-nadi, or into sushumna. Yogi must perform mula-bandha daily and often.

"Yoga-Kundalini Upanishad"

387. The yogi is the one who sits in baddha-padmasana, holds apana-vayu (mula-bandha), and then raises it through sushumna into the akasha area where Shiva lives. Blessed is the one who has experienced this.

"Shiva-svarodaya"

122. Mula-bandha - the root lock connects prana with apana in the navel area (here is the entrance to the sushumna), through this exercise the fruits of yoga are obtained.

«Yoga-tattva-upanisad»

3.60. And this is mula-bandha. Tightly pressing yoni with the heel, compress the anus and raise the apana up. This is how mula-bandha is performed.
3.61. With the compression of the muladhara, apana, which is below, rises upward. Therefore, yogis call it mula-bandha (lock of muladhara).
3.62. Pressing yoni (perineum), again and again with force drive up air.
3.63. Mula-bandha connects prana and apana, nadi and bindu and gives yogi an unconditional success.
3.64. The mix of prana and apana reduces the amount of urine and feces, and the old man becomes young.
3.65. Apana rises up, reaches the agni-mandala and flames flare up.
3.66. Fire and apana connect with prana, whose nature is fire. The heat of the body becomes bright and strong.
3.67. Then Kundalini, feeling the heat, wakes up from sleep, like a snake hit with a stick hissing and straightening.
3.68. Then she enters brahma-nadi (sushumna). Yogi must always practice mula-bandha.

«Hatha-yoga-pradipika»

This bandha is associated with mula-adhara, relates to shakti-pith Kamarupa, and also to Brahma-granthi (it is believed that mula-bandha helps unleash this knot).