Objective: To investigate if McKenzie exercises when applied to a cohort of patients with chronic LBP who have a directional preference demonstrate improved recruitment of the transversus abdominis compared to motor control exercises when measurements were assessed from ultrasound images. Design: A randomized blinded trial with a 12-month follow-up. Setting: The Physiotherapy department of Concord Hospital a primary health care environment. Participants: 70-adults with greater than three-month history of LBP who have a directional preference. Interventions: McKenzie techniques or motor control exercises for 12-sessions over eight weeks. Main outcome measures: Transversus abdominus thickness measured from real time ultrasound images, pain, global perceived effect and capacity to self-manage. Discussion: This study will be the first to investigate the possible mechanism of action that McKenzie therapy and motor control exercises have on the recruitment of the transversus abdominus in a cohort of low back pain patients sub-classified with a directional preference. Patients receiving matched exercises according to their directional preference are believed to have better outcomes than those receiving unmatched exercises. A better understanding of the mechanism of action that specific treatments such as motor control exercises or McKenzie exercises have on patients classified with a directional preference will allow therapist to make a more informed choice about treatment options.