Progressive muscle relaxation (PMR) is a technique for learning to monitor and control the state of muscular tension. It was developed by American physician Edmund Jacobson in the early 1920s. Jacobson wrote several books on the subject.
The technique involves learning to monitor tension in each specific muscle group in the body by deliberately inducing tension in each group. This tension is then released, with attention paid to the contrast between tension and relaxation.
A modification of the technique is "biofeedback" in which one uses external measuring devices to indicate how successful one is in relaxing and then to use those techniques to relax without the help of external measuring devices.
These learning sessions are not exercises or self-hypnosis. Training sessions are conducted in a darkened room with the learner in a reclined position and eyes closed. The instructions begin by telling the person to relax and just let go, detaching from thoughts or physical distractions or trying to solve problems. In each session the teacher reviews tensing one particular muscle group. If the student is slow in learning how to let the tension go for a particular muscle group, that group is focused on in the next session. The learner is told to continue to practice the relaxation technique in their daily lives. It is not our natural response to relax when there is an external or internal stimulant. However, as in many other physical conditions that we have no control over, the body's best response would be no response at all.
Jacobson's progressive relaxation has remained popular with modern physical therapists.
Progressive muscle relaxation is also touted as a method of treating insomnia. It addresses some causes of insomnia: physical tension, restlessness, and racing thoughts. The technique directly acts on the physical level, but the need to focus on the steps can also displace racing thoughts.
WebMD says,
"Most practitioners recommend tensing and relaxing the muscle groups one at a time in a specific order, generally beginning with the lower extremities and ending with the face, abdomen, and chest."
"While inhaling, contract one muscle group (for example your upper thighs) for 5 seconds to 10 seconds, then exhale and suddenly release the tension in that muscle group. Give yourself 10 seconds to 20 seconds to relax, and then move on to the next muscle group (for example your buttocks)."