Intramuscular therapy (also known as dry needling) has been shown to give dramatic relief of musculoskeletal pain. The mechanisms of action remain unknown, and this study will examine for a neurophysiological effect.

Consenting adults will be taught how to contract their abdominal muscles, and to contract transversus abdominis in particular. They will then have real time ultrasound measurements of the resting and contracted thickness of their left transversus abdominis muscle. After this, they will receive actual or sham needling to their left multifidus muscle by another researchers blinded to the real time ultrasound measurements. After needling or sham intervention is complete, the original researchers will return to re-measure transversus abdominis. They will be blind to intervention allocation.

Inclusion Criteria:

• Age, absence of back pain or symptoms for greater than 6 months and ability to perform DCC. Subjects must also report they are comfortable with being 'needled'.

Exclusion Criteria:

• Presence of back pain or symptoms within the last 6 months, history of: abdominal or spinal surgery, significant scoliosis, rheumatoid arthritis, osteoporosis, osteopenia, active ankylosing spondylitis. If a subject reports a fear of needles.