They say 30 minutes of Yoga Nidra is equal to four hours of deep sleep and completely resets be nervous system.
Yoga Nidra, which is derived from the tantras, is a powerful technique in which you learn to relax consciously. In yoga nidra, sleep is not regarded as relaxation. People feel that they are relaxing when the collapse in an easy chair with a cup of coffee, a drink or a cigarette, and read a newspaper or switch on the television. But this will never suffice as a scientific definition of relaxation. These are only sensory diversions. True relaxation is actually an experience far beyond all this. For absolute relaxation you must remain aware. This is yoga nidra, the state of dynamic sleep.
-Swami Satyananda Saraswati from Yoga Nidra
Yoga Nidra helps to bring the nervous system, among many other aspects of our being, into balance. Through evolution and the modernization of our culture we spend much of our time utilizing our sympathetic nervous system. Though this is a very important part of human biology, in Yoga we are always striving for balance. When ones nervous system is out of balance in can lead to a host of physical and mental ailments. Yoga Nidra is an amazing practice that restores homeostasis. It can be used to great benefit even when a physical practice is not possible or advisable.