Yoga Nidra (or Yogic sleep) is guided meditation, a voice (recorded or live) guide you through a deep state of relaxation while you remain fully conscious. One hour of Yogic sleep is believed to be as restorative as three hours of regular sleep & I can’t argue that. Whenever I need a good rest but don’t have much time, or being in well need of stressing down & releasing tension I resort to this method of relaxation. I make sure to set my alarm clock in case I fall asleep which I do on occasion & also check the house to make sure the front door is locked, the stove isn’t on by accident & etcetera to ensure safety and that I will be able to be as relaxed as possible to get the most out of my yogic sleep. There are many benefits of resting well and releasing tension so I can only recommend it.
For me it’s important that the voice of the person who is guiding my yogic sleep is one which is pleasant & soothing. I find Shar Hills one of the better guides, there are three of her audio files available to stream online or download at the following link: http://www.5809yoga.com/yoga-nidra.html
Kaman Desai of the Amrit Yoga Institute explains yogic sleep & what the possibilities are in the video below.
Yoga Nidra or “yogic sleep” is a sleep-like state which yogis report to experience during their meditations. Yoga nidra, lucid sleeping is among the deepest possible states of relaxation while still maintaining full consciousness. (Lucid dreaming is an unrelated phenomenon.) The distinguishing difference is the degree to which one remains cognisant of the actual physical environment as opposed to a dream environment. In lucid dreaming, one is only (or mainly) cognisant of the dream environment, and have little or no awareness of our actual environment.
The practice of yoga relaxation has been found to reduce tension and anxiety. The autonomic symptoms of high anxiety such as headache, giddiness, chest pain, palpitations, sweating and abdominal pain respond well. It has been used to help soldiers from war cope with posttraumatic stress disorder(PTSD).
Source & extended information: http://en.wikipedia.org/wiki/Yoga_nidra