The Alexander Technique is a technique of body re-education and coordination, accomplished through physical and psychological principles. The technique focuses on the self-perception of body use and may be promoted for the alleviation of back pain, rehabilitation after accidents, improving breathing, playing musical instruments, acting, and singing.

The technique takes its name from F. Matthias Alexander, who first formulated its principles between 1890 and 1900. Alexander developed the Technique as a personal tool to alleviate pain and hoarseness that affected his ability to pursue a career as a Shakespearean actor. Alexander taught his technique to individuals for 30 years before creating a school to train other teachers in the technique. The Society of Teachers of The Alexander Technique and its affiliates certify Alexander Technique teachers after successfully completing a 1600-hour 3-year curriculum with teaching strategies traced to Alexander.

Historically taught in private lessons which may last from 30 minutes to an hour, the instructor uses observation and light hand contact with the student to detect stressful movements and body usage. Students are guided by the teacher through demonstration, verbal explanation, and conscious examination of their movement and posture to inhibit habitual reactions and learn newer and more efficient ways to perform tasks like walking, standing, and sitting.

Its principles have also been adapted to be taught in groups, often using short individual lessons in front of the group which act as examples to the class.
Source: http://en.wikipedia.org/w/index.php?title=Alexander+Technique