P2.193 Thursday, Jan. 5 Epaxial muscle function in walking and running humans SCHILLING, N.*; CARRIER, D.R.; ANDERS, C.; Small Animal Clinic, University of Veterinary Medicine Hannover; Department of Biology, University of Utah; Clinic for Trauma, Hand and reconstructive Surgery, University Hospital Jena email@example.com
During locomotion, human epaxial muscles have been suggested to 1) dynamically stabilize the trunk in the frontal and the sagittal planes during walking, 2) primarily control trunk motions in the sagittal plane during running, and 3) mobilize the trunk in the sagittal and the transverse planes during walking. In this study, we tested an additional hypothesis. Based on observations in quadrupedal mammals, 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.