Recently, physical therapists have begun treating people who have mechanical low back pain, hypothesized to be caused by segmental instability in the lumbar spine, with a very specific exercise program consisting of trunk stabilization exercises. The theory behind the use of trunk stabilization exercises to treat lower back pain is that active contraction of the trunk local segmental muscles helps to control inter-segmental movement in the spine. The initial trunk stabilization exercise that physical therapists teach patients is an abdominal drawing in maneuver often called an abdominal hollowing exercise (AHE). A challenge for physical therapists is to establish the most effective means of teaching people to contract the relevant muscles needed to perform the AHE. The purpose of this study is to examine if supplementing the typical clinical instruction for teaching the AHE with visual ultrasound feedback to the patient is effective at reducing the length of time it takes an individual to learn to perform an AHE.