This lock is to be applied in all chanting meditations, during most pranayam exercises and whenever you hold the breath in or out.
The purpose is to seal the energy that is generated in the upper areas of your brain stem.
It also prevents undue changes in blood pressure that can be induced by exercise and breathing, regulates blood pressure and rids one of many dizziness, creates nerve reflexes that stimulate and balance the thyroid and parathyroid glands, directs the flow of pranic energy into the central channel past the neck and in the central channel to the heart and allows you to focus on internal sensations and perceptions without distraction.
Method:
Sit comfortably with straight spine.
Lift the chest and sternum upward.
At the same time gently stretch the back of your neck straight by pulling your chin toward the back of your neck.
Keep your head level, straight and centered.
Keep your muscles in your neck, throat face and brow relaxed.
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