title: Spinal lordosis optimizes the requirements for a stable erect posture.
abstract: BACKGROUND
  Lordosis is the bending of the lumbar spine that gives the vertebral column of humans its characteristic ventrally convex curvature. Infants develop lordosis around the time when they acquire bipedal locomotion. Even macaques develop a lordosis when they are trained to walk bipedally. The aim of this study was to investigate why humans and some animals develop a lumbar lordosis while learning to walk bipedally.
  
  
  RESULTS
  We developed a musculoskeletal model of the lumbar spine, that includes an asymmetric, dorsally shifted location of the spinal column in the body, realistic moment arms, and physiological cross-sectional areas (PCSA) of the muscles as well as realistic force-length and force-velocity relationships. The model was used to analyze the stability of an upright body posture. According to our results, lordosis reduces the local joint torques necessary for an equilibrium of the vertebral column during an erect posture. At the same time lordosis increases the demands on the global muscles to provide stability.
  
  
  CONCLUSIONS
  We conclude that the development of a spinal lordosis is a compromise between the stability requirements of an erect posture and the necessity of torque equilibria at each spinal segment.
authors.affiliation: Motion Science, Westf, Wilhelms-Universität Münster, Horstmarer Landweg 62b, 48149 Münster. heiko.wagner@wwu.de
authors.forename: Heiko
authors.initials: H
authors.lastname: Wagner
authors.forename: Anne
authors.initials: A
authors.lastname: Liebetrau
authors.forename: David
authors.initials: D
authors.lastname: Schinowski
authors.forename: Thomas
authors.initials: T
authors.lastname: Wulf
authors.forename: Marc H E
authors.initials: MH
authors.lastname: de Lussanet
mesh_terms: D006801:Humans; D008141:Lordosis; D008159:Lumbar Vertebrae; D008954:Models, Biological; D011187:Posture; D019415:Torque