Low back pain (LBP), a highly prevalent problem in society, is often a recurrent condition. Recent advances in the understanding of the biomechanics of LBP have highlighted the importance of muscular stabilization of the "neutral zone" range of motion in the low back. The lumbar multifidus muscles (LMM) are important stabilizers of this neutral zone, and dysfunction in these muscles is strongly associated with LBP. The dysfunction is a result of pain inhibition from the spine, and it tends to continue even after the pain has resolved, likely contributing to the high recurrence rate of LBP. Persisting LMM dysfunction is identified by atrophic replacement of multifidus muscle with fat, a condition that is best seen on magnetic resonance imaging. Muscle training directed at teaching patients to activate their LMM is an important feature of any clinical approach to the LBP patient with demonstrated LMM dysfunction or atrophy.