The purpose of this study is to understand how different physical therapy interventions affect the use of certain abdominal muscles in patients with low back pain.

Patients with low back pain will undergo ultrasound imaging of the lateral abdominal wall to measure resting and contracted thickness of the transversus abdominis muscle. Following the pre-intervention measurement, patients will receive one of two physical therapy interventions (side lying thrust joint manipulation or side lying non-thrust oscillations into slight rotation) which will have been randomly assigned. Immediately after intervention, ultrasound imaging will be repeated on the resting and contracted thickness of the transversus abdominis.

Inclusion Criteria:

• Currently receiving physical therapy treatment for back pain or back pain symptoms
• 18-70 years of age
• Able to perform the abdominal drawing in maneuver

Exclusion Criteria:

• Presence of a serious pathology
• Diagnosis of spinal stenosis or symptoms in both lower legs (changes in sensation, muscle weakness)
• Any history of low back surgery, rheumatoid arthritis, osteoporosis, osteopenia, or ankylosing spondylitis