Progressive muscle relaxation is a systematic technique developed in the 1930s by Dr. Edmund Jacobson to reduce stress and induce deep relaxation. It works by having users sequentially tense and relax different muscle groups in the body to produce a "relaxation response" that counters the body's stressed "fight or flight" state. Regular practice can help decrease anxiety, improve mood and concentration, and increase feelings of control and self-esteem. The technique involves tensing and relaxing muscles from the hands and arms to the legs and toes over 20-30 minutes to induce a state of full body relaxation.