After completing a basic program in massage therapy, Craig Williamson opened his first private practice on Nantucket Island, Massachusetts, in 1980.

The first significant influence on his work was at the Lomi School, in San Francisco, where Craig completed both the Lomi Bodywork training and the Lomi School Psychotherapy for Bodyworkers Program. The Lomi School was founded by a small group of pioneers in the bodywork and human potential fields. Among these remarkable people were Robert Hall, M.D., an original student of both Ida Rolf and Fritz Perls; Richard Strozzi Heckler, Aikido teacher; and Catherine Flaxman, a psychotherapist, writer and dancer.

Craig’s education continued throughout the 1980s and 1990s. During that time he studied numerous hands-on manipulative techniques, including neuromuscular therapy and myofascial manipulation. He also began what became a continuous study of movement-reeducation methods, which included the Alexander TechniqueIdeokinesis (the work of Mabel Todd and her students), and Feldenkrais. For a number of years Craig also studied contact improvisation with Sara Shelton Mann in San Francisco, and Bharat Natyam with Neena Gulati in Boston.

In the mid 1980’s Craig met Maria Schnaitman while on a short vacation in Maine. Maria Schnaitman, a gifted physiotherapist and breath therapist in Germany in the 1920s and 1930s, had developed a unique method of helping people to regain their natural patterns of movement by improving sensory awareness. The primary influence on her early education was Elsa Gindler, who is now recognized as the pioneer of body work and sensory awareness training in Europe in the early 20th century. Maria was personal friends with Karl Durkheim, a German psychotherapist and zen teacher who is considered responsible for bringing zen philosophy into the American mainstream in the mid-20th century. Durkheim was the author of a number of books, but it was his book Hara: The Vital Center of Man that most influenced Maria's work. His comment about her work after he received a breathing treatment from her was "this is zen." She spoke with Durkheim regularly by phone until his death in 1988.

Maria Schnaitman had an exceptional ability to know the basis of a person's somatic problem by observing their carriage, movement, breathing, and speech. Her work involved hands-on treatment as well as movement exercise. Craig eventually moved to Maine and worked regularly with Maria, who lived in the coastal town of Boothbay. Craig coaxed her out of retirement, to become the only person she trained in her methods. His apprenticeship with her lasted until she died in 2000, at the age of 90.

By the early 1990s Craig had developed his own way of helping people who came to see him for musculoskeletal pain problems. This involved a synthesis of corrective movement exercises and kinesthetic awareness techniques he had either devised himself or learned along the way. It also involved a new hands-on method that combined active neuromuscular retraining with myofascial manipulation. Craig then began teaching his therapeutic approach to massage therapists and physical therapists, as well as to musicians and other performers. He originally referred to this approach Somatic Integration. The term somatic, which means "bodily," was championed by Thomas Hanna who used it to mean “the body as experienced from within.” The definition of somatic integration is: a neuromuscular and psychophysical approach to addressing problems with bodily pain, movement and carriage. Craig later renamed his method Williamson Muscular Retraining. 

In 1998 Craig received a Master of Science in Occupational Therapy from Boston University. He has a private practice in Portland, Maine where he  uses Williamson Muscular Retraining exclusively to help people with all manner of musculoskeletal pain, movement, and alignment problems.

Craig has been an adjunct faculty in the Theater/Dance department at Bowdoin College, where he taught Bodywork for Performers (DANCE 115). He continues to be an adjunct faculty at the University of Southern Maine School of Music in Portland, Maine, where he teaches Dynamic Posture and Alignment (MUS 109).