The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)

Epaxial muscle function in walking and running humans


1University of Veterinary Medicine Hannover, Foundation, Small Animal Clinic, 2Friedrich-Schiller-University Jena, Institute of Systematic Zoology and Evolutionary Biology, 3University of Utah, Department of Biology, 4University Hospital Jena, Clinic for Trauma, Hand and Reconstructive Surgery

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During locomotion, human epaxial muscles have been suggested to 1) dynamically stabilize the trunk in the frontal and sagittal planes during walking, 2) primarily control trunk motions in the sagittal plane during running, and 3) mobilize the trunk in the sagittal and transverse planes during walking. In this study, we tested an additional hypothesis. We hypothesized that the human epaxial muscles of humans also function to dynamically stabilize the pelvic girdle against the action of the extrinsic limb muscles and thus provide a firm base for their activity during locomotion. To test this, we manipulated the locomotor forces acting on the trunk and the limbs by having subjects walk and run at three different speeds and inclinations and measured the activity of two epaxial muscles, the m. longissimus thoracis and the m. multifidus lumborum, and six extrinsic limb muscles in seventeen healthy male subjects. Additionally, we recorded the activity of five intrinsic limb muscles to assess whether the epaxial muscles also function in the vertical support of the body. Using correlation analysis, we tested if the changes in the activation patterns of the extrinsic and intrinsic limb muscles associated with changes in gait, speed or inclination were met by corresponding changes in the activation patterns of the ipsilateral and/or the contralateral epaxial muscles. Our results are consistent with the human epaxial muscles providing dynamic stability of the pelvis against the actions of the contralateral retractor and the ipsilateral protractor muscles as well as providing vertical support of the body.

This research was supported by grants from The Center of Interdisciplinary Prevention of Diseases related to Professional Activities funded by the Friedrich-Schiller University Jena and the Berufsgenossenschaft Nahrungsmittel und Gastgewerbe Erfurt and The National Science Foundation (IOS-0817782)

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