What is a Bandha?
In Sanskrit: Bandha means to bind, capture or hold. It is a way Yoga practitioners prevent energy escaping when performing pranayama the ancient art of yoga breathing exercise.
How do you perform the bandhas?
There are 3 Bandhas:
Jalandhara bandha 
performed by dropping the chin to the chest while not hunching (Kyphosis) the upper back and shoulders forward. The neck muscles need to be flexible to perform this tilt.
Stops energy escaping upwards past the neck.
Uddiyana Bandha Performed by expelling all the air and drawing the addomin and diaphragm up to the chest. Do this progressively as it tenses the mind and temples.
Stops energy escaping around the abdonin.
Mulabandha Performed by clenching the pelvic floor muscles. ie Holding in the need to use the toilet and evacualte the bowels. Do it lightly or it tenses the nerves above.
Stops energy from escaping downwards through the Tailbone ( Coccyx).
