In this presentation, Dr. Lothe Raven discusses his thirteen years of research on the neurophysiological properties of back muscles, with a special focus on the role of the Multifidus muscle. This session will delve into the anatomy of deep axial muscles, motoneurons as the final common pathway, and the normal firing characteristics and postural role of the multifidus muscle. This leads to a description of what changes in neurophysiology and spinal biomechanics may follow a chiropractic adjustment; thus, he examines the effect of spinal manipulation on spinal function and multifidus activity.