A Bandha is a subtle energetic action or lock with the intention of retaining and directing prana (energy) in the body. The use of Bandha intensifies the agni, and specifically creates Agni and moves prana within the subtle body. Bandha is to be studied and practiced with a teacher.
There are three main locks or Bandhas. They are the Jalandhara Bandha, Uddiyana Bandha, and the Mula Bandha. Jalandhara Bandha is physical and energetic lock at the throat. Uddiyana Bandha focus in the area between the diaphragm and the pelvic floor. Mula Bandha concentrates on the area between the navel and the pelvic floor. Employing all three of the locks creates the great seal of Maha Bandha.
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