Progressive Neuromuscular Relaxation Explanation

The following explanation of PNR has been taken from http://faculty.weber.edu/molpin/healthclasses/1110/bookchapters/progress...
For further reading on the topic please visit the site.

"Many muscles in the body remain in a chronically contracted state because they are continuously receiving the message from the nervous system that they should be contracting in order to fight or run from the big bear. They don't receive the signal from the nervous system that the threat has passed and it is okay to relax. An example of this is often found in a person's shoulders. They might feel tight and sore because these muscles are continually tensed. It was a man named Edmond Jacobson who in 1929 first caught on to this idea of tension and relaxation in the muscles. He was a doctor living in Chicago working with patients who suffered from a variety of maladies. He noticed one common characteristic of nearly all of his patients and that was muscle tension. Working with his patients, he found that they were able to diminish the severity of the disorder as they were able to reduce or relieve muscle tension. Jacobson found that most of his patients had no idea that they had excess muscle tension in various places in their bodies. He found that as his patients were asked to consciously flex these tensed up areas, and then consciously relieve that tension, the contracting muscles would become relaxed. Jacobson understood that a muscle cannot be contracting and relaxing at the same time and by forcibly tensing a muscle and then consciously releasing the contraction, the muscles would naturally return to their naturally relaxed position. Thus was born the relaxation technique called Progressive Muscular Relaxation (PMR). It has also been called Progressive Neuromuscular Relaxation identifying the autonomic nervous system activity in initiating and turning off muscle tension. Another name for PMR is Active Progressive Relaxation. Progressive relaxation is probably the most commonly used form of relaxation therapy in western society today."