the Yogic contraction holding the breath and placing the chin on the chest

Means, “chin lock.” Practiced during certain stages of kumbhaka (breath retention). A more advanced version in the AYP lessons is called dynamic jalandhara, or chin pump.

The bandha located at the throat chakra. Jalandhara bandha is physically engaged when we draw the chin towards the collarbone and lift the chest. This lock is stimulating to the parathyroid, and thyroid glands. It also is important to engage as it protects the subtle network of nerves in the neck region, otherwise the energy shooting up our spine may be too powerful and damage may occur to those nerves. It is our lid on our "kundalini Cola!"