Reflex relationships of paravertebral muscles

¹ Department of Physiology and Pharmacology, Kirksville College of Osteopathy and Surgery, Kirksville, Missouri

The muscles of the back are shown to function reflexly in various antagonistic and synergistic pairs. Intertransversales muscles of opposite sides can act synergistically for ventral flexion or antagonistically for lateral flexion. Multifidus muscles of opposite sides act independently or synergistically only. There is a stronger reciprocal relationship between the multifidus on one side and the intertransversales of the other side than between multifidus and intertransversales of the same side. Inhibition of antagonists occurs with stimuli too weak to excite the agonists. The patterns of the spinal reflex responses of the paravertebral musculature to cutaneous stimulation change with regard to segmented level and to area of skin stimulated. Stimulation of dorsal skin provokes reflex contraction of the multifidus muscles. Stimulation of ventral skin provokes reflex contraction of the intertransversales muscles. A stimulus applied to a lateral skin area elicits a response in both members of this antagonistic pair. Moving the dorsal stimulus caudally from L-5 to L-6 results in a change of the reflex pattern from multifidus activity to intertransversales activity.