Most bilaterian animals are able to use active locomotion to open up its own habitat. Among vertebrates locomotion evolved from lateral undulation of the body axis in fishes up to the axial and leg movements in tetrapods. Major reorganisations of the trunk's musculature are involved in these evolutionary changes.The present morphological and physiological study was carried out to compare the structure and function of back muscles between humans and other mammals. Microscopic dissections of the intramuscular innervation uncover a segmental nervous supply of all epaxial muscles of the rat. It was possible to demonstrate these compartmentalisation by using topographical surface-EMGs. During runnig on a treadmill the activity of the multifidus muscles on both body sides were measured with 16 and 32 channel-matrix-electrodes. The movement of the animals was recorded synchronously by a high-speed camera system. A biphasic activation pattern was observed in both multifidus muscles. During touch down of the hindlimbs the ipsilateral muscle is always more activated than the muscle of the contralateral body side. It is astonishing that the activation pattern of the human multifidus muscle is very similar in spite of the evolution of bipedal locomotion. Supported by KIP, Univ. Jena BGN.