Stress is a cognitive or emotional response made by the individual towards any situation, which demands adjustment. Udupa (1978) suggests that stress-related disorders evolve gradually through four stages. In the first stage, psychological symptoms like anxiety and irritability arise due to over activation of the sympathetic nervous system. The second stage is characterized by related physical symptoms like high blood pressure, increased heart rate etc. In the third stage, the abnormalities manifest clinically in the organ systems. In the last stage, severe symptoms in particular organs result which need long-term medical management.
Scientists are taking advantage of new technologies to see exactly what goes on inside the brains of Yoga nidra practitioners. The neuroscientists hypothesize that regular meditation actually alters the way the brain is wired, and that these changes could be at the heart of claims that meditation can improve health and well-being. But the rigors of the scientific method might never have been applied to studying the practice of meditation.
Modern psychology as well as yogic philosophy believes in three kinds of tension - muscular tensions, emotional tensions and mental tensions - which can be progressively released through the systematic and regular practice of Yoga and Meditation. Muscular tension results from nervous and endocrinal imbalances. It manifests in the form of stiffness and rigidity in the physical body. In the practice of Meditation the body is progressively relaxed, which in turn releases the accumulated muscular tensions.
Yoga nidra is probably best-known technique to induce complete physical mental and emotional relaxation. Yoga nidra is a state of consciousness, which is, neither sleep nor awaken, neither is it concentration nor hypnotism. It can be defined, as an altered state of consciousness
Swami Rama (1998) is a state between sleep and Samadhi. It is a half- sleep and half waking state: it is not a waking state, and it is not really a sleep state. Yoga nidra is a state of conscious sleep in which one can record what is going on. There is a fine demarcation between Yoga nidra and Samadhi. In yoga nidra one can record those which he cannot receive in the conscious state. When one cannot register something properly in the waking state, they can go into yoga nidra to register it.
Sri Ram Sharma Acharya (1995) Yoga nidra can be understood as scientific sleep. It is a total practice of yoga it self. The practice of Yoga nidra on the contrary allows one to attain a state of ‘awakened’ sleep. In this state, the body and the external mind (and hence the thought process) are made to sleep as per the order of the inner will. The determination, the willpower of the individual self remain active in this state and endeavor auto- suggestive experience of the power of the unconscious mind and its linkage with the soul.
Sw. Satyananda Saraswati (1975) explains Yoga nidra as a state of mind between wakefulness and dream. When someone practices Yoga nidra he opens the deeper phases of the mind. During the practice of Yoga nidra the consciousness is at different levels. Sometimes it is very close to the senses and at others, it is at a very remote distance. When the consciousness is at a remote distances. It is only possible to understand through the auditory channels. During Yoga nidra the consciousness is suspended for a few moments periodically, which means that it alternates between the subconscious and unconscious states. For the practice of Yoga nidra one should lie flat on his back and follow the spoken instruction of yoga instructor. It is convenient to use Yoga nidra tape. During the practice there should be no movement by the practitioner, as well as he should try to remain awake and aware of every given instruction.
Various studies have been done in different part of world for observing the effect of Yoga nidra. M.J. Cooper, (1979): in an important study at the University of Tel Aviv (Israel) says that Yoga nidra significantly lowered levels of serum cholesterol in cardiac patients. Erskine-Milliss, J. & Schonell, M., (1981) states that, the future role of Yoga nidra in coronary care and management regimes appears to be a major one. The value of the practice of yogic relaxation in prevention of cardiovascular disease has been fairly well recognized and accepted.
Sw. Mangalteertham (1998) proved through a series of study done at Cherring Cross Medical School London that it is a technique in which one can alter the states of consciousness from beta to alpha and then to delta. Therefore subject enjoys the different state of consciousness, knowingly. It is a pratyahara but also opens the door for meditation. Sharma, N. R. Yadava, A. Hooda, D. (2005) observed that practice of Yoga brings a harmony in psycho-physiology of the practitioners.
Deuskar, M. Poonawala, N. Bhatewara, S. A. (2006) fined a significant change in the performance of archers due to the practice of Yoga nidra. Kumar, Kamakhya (2008) observed a significant change in the stress level in his study. Result shows that Yoga nidra positively decrease the stress level of the male and female subjects both.
There is no question about the close relation between the body and the brain. Various centers in the brain control, modify, and affect our bodily functions. In fact, there is a center in the brain for every act, whether willful or reflex, physical or mental. Experimental data have identified many such specific centers. Stimulation of these centers leads to appropriate actions, be they motor or sensory, secretary or emotive, affective or cognitive. Thus we have a holographic representation of the body on the brain.
In Yoga nidra exactly opposite process is used to make the brain centers active by focusing awareness on the parts of the body in a definite sequence. Thus, the person tries to stimulate various parts of the brain by focusing the awareness on the corresponding parts of the body. By awareness is meant 'attitude of witness' towards physical or mental actions of the body. This stimulation ultimately results into relaxation and a reduction at Psycho-physiological level particularly stress in the practitioners of Yoga nidra.When the individual fails to adjust to the situation, only then distress results. Some individuals are prone to developing distress due to their unconscious urge to remain tense. When distress continues for a long period, it may result in psychological disorders like neuroses or even psychoses. In the practice of Yoga nidra, the inherent tendency to become tense is rooted out and the individual starts viewing the situation as less demanding. Gersten (1978) said that the practitioner of Yoga nidra becomes his own psychotherapist, recognizing and systematically alleviating his own personal problems and interpersonal difficulties. It can be concluded that the practitioners of Yoga nidra becomes his own psychotherapist to manage his stress to live a stress free life.