title: Morphology and motion: hindlimb proportions and swing phase kinematics in terrestrially locomoting charadriiform birds.
abstract: Differing limb proportions in terms of length and mass, as well as differences in mass being concentrated proximally or distally, influence the limb's moment of inertia (MOI), which represents its resistance to being swung. Limb morphology - including limb segment proportions - thus probably has direct relevance for the metabolic cost of swinging the limb during locomotion. However, it remains largely unexplored how differences in limb proportions influence limb kinematics during swing phase. To test whether differences in limb proportions are associated with differences in swing phase kinematics, we collected hindlimb kinematic data from three species of charadriiform birds differing widely in their hindlimb proportions: lapwings, oystercatchers and avocets. Using these three species, we tested for differences in maximum joint flexion, maximum joint extension and range of motion (RoM), in addition to differences in maximum segment angular velocity and excursion. We found that the taxa with greater limb MOI - oystercatchers and avocets - flex their limbs more than lapwings. However, we found no consistent differences in joint extension and RoM among species. Likewise, we found no consistent differences in limb segment angular velocity and excursion, indicating that differences in limb inertia in these three avian species do not necessarily underlie the rate or extent of limb segment movements. The observed increased limb flexion among these taxa with distally heavy limbs resulted in reduced MOI of the limb when compared with a neutral pose. A trade-off between exerting force to actively flex the limb and potential savings by a reduction of MOI is skewed towards reducing the limb's MOI as a result of MOI being in part a function of the radius of gyration squared. Increased limb flexion is a likely means to lower the cost of swinging the limbs.
authors.affiliation: Institut für Spezielle Zoologie und Evolutionsbiologie, Friedrich-Schiller-Universität Jena, Erbertstraße 1, Jena 00743, Germany College for Life Sciences, Wissenschaftskolleg zu Berlin, Wallotstraße 19, Berlin 14193, Germany Museum für Naturkunde Berlin, Invalidenstraße 43, Berlin 10115, Germany brandon.kilbourne@mfn-berlin.de.
authors.forename: Brandon M
authors.initials: BM
authors.lastname: Kilbourne
authors.affiliation: Institut für Spezielle Zoologie und Evolutionsbiologie, Friedrich-Schiller-Universität Jena, Erbertstraße 1, Jena 00743, Germany.
authors.forename: Emanuel
authors.initials: E
authors.lastname: Andrada
authors.affiliation: Institut für Spezielle Zoologie und Evolutionsbiologie, Friedrich-Schiller-Universität Jena, Erbertstraße 1, Jena 00743, Germany.
authors.forename: Martin S
authors.initials: MS
authors.lastname: Fischer
authors.affiliation: Institut für Spezielle Zoologie und Evolutionsbiologie, Friedrich-Schiller-Universität Jena, Erbertstraße 1, Jena 00743, Germany Image Knowledge Gestaltung - an Interdisciplinary Laboratory, Humboldt-Universität zu Berlin, Unter den Linden 6, Berlin 10099, Germany Institute of Biology, Humboldt-Universität zu Berlin, Philippstraße 13, Berlin 10115, Germany.
authors.forename: John A
authors.initials: JA
authors.lastname: Nyakatura
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D046091:Charadriiformes / Q000033:anatomy & histology / Q000502:physiology*; D006614:Hindlimb / Q000033:anatomy & histology / Q000502:physiology*; D008124:Locomotion; D016059:Range of Motion, Articular
keywords: Charadriiformes; Kinematics; Limb segments; Locomotion; Moment of inertia; Trade-off