While most consider meditation to be a purely spiritual exercise, the reality, as determined within the past several decades by medical researchers, is that the practice also bestows upon its practitioners many physical health benefits. In various forms of meditation, one relaxes the body while freeing the mind from distracting thoughts, such as the events of the day, and to-do lists. This is achieved by being mindful of one's breathing, or repetition of a word or sound to keep distracting thoughts from the mind. The latter is a Hindu concept. Regardless of the type of meditation, there have been studies that show changes in the body during meditation and immediately after meditating. Conjecture by the National Institutes of Health indicates that meditation may work to benefit one's physical health by affecting the involuntary nervous system, the system that regulates organs and muscles that control involuntary functions such as breathing, digestions, heartbeat, and sweating. It is the effect of meditation on the nervous system that intrigues researchers the most. The sympathetic nervous system is that which creates the "fight or flight" response, whereby heart rate and breathing quicken and blood vessels narrow, thus restricting blood flow. The parasympathetic nervous system, on the other hand, causes the heart rate and breathing to slow down, resulting in dilated blood vessels that lead to improved blood flow. A meditative state actually does slow heart rate and breathing, thus improving blood flow and digestion. Meditation can be thought of as a temporary improvement in the overall functioning of the body. Because meditation is also believed to improve one's ability to concentrate, it can condition the body and mind to deal with stressful situations in a manner different than the natural tendency. While the fight or flight instinct cannot be removed from one's physiological makeup, meditation can be thought of as a sort of training for well-being. Of the specific health benefits that the NIH and other reputable sources note as being potentially attributable to meditation are the following: • Anxiety reduction. • Pain reduction. • Lessening of depression symptoms. • Decreased stress. • Overcoming insomnia. • Lessening of symptoms of chronic illnesses such as heart disease, cancer, HIV/AIDS and others. • Decreased blood pressure. • Decreased standing heart rate. • Reduction of free radicals that cause tissue damage. • Drop in cholesterol levels. • Improved air flow to the lungs. All of this does not even address the mental and emotional benefits of meditation, though another interesting area of study among medical researchers is the degree to which humans can actually lessen physical symptoms by a positive mental outlook.