Scale effects between body size and limb design in quadrupedal mammals

PLoS One. 2013 Nov 8;8(11):e78392. doi: 10.1371/journal.pone.0078392. eCollection 2013.


Recently the metabolic cost of swinging the limbs has been found to be much greater than previously thought, raising the possibility that limb rotational inertia influences the energetics of locomotion. Larger mammals have a lower mass-specific cost of transport than smaller mammals. The scaling of the mass-specific cost of transport is partly explained by decreasing stride frequency with increasing body size; however, it is unknown if limb rotational inertia also influences the mass-specific cost of transport. Limb length and inertial properties--limb mass, center of mass (COM) position, moment of inertia, radius of gyration, and natural frequency--were measured in 44 species of terrestrial mammals, spanning eight taxonomic orders. Limb length increases disproportionately with body mass via positive allometry (length ∝ body mass(0.40)); the positive allometry of limb length may help explain the scaling of the metabolic cost of transport. When scaled against body mass, forelimb inertial properties, apart from mass, scale with positive allometry. Fore- and hindlimb mass scale according to geometric similarity (limb mass ∝ body mass(1.0)), as do the remaining hindlimb inertial properties. The positive allometry of limb length is largely the result of absolute differences in limb inertial properties between mammalian subgroups. Though likely detrimental to locomotor costs in large mammals, scale effects in limb inertial properties appear to be concomitant with scale effects in sensorimotor control and locomotor ability in terrestrial mammals. Across mammals, the forelimb's potential for angular acceleration scales according to geometric similarity, whereas the hindlimb's potential for angular acceleration scales with positive allometry.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Body Size / physiology*
  • Hindlimb* / anatomy & histology
  • Hindlimb* / physiology
  • Mammals* / anatomy & histology
  • Mammals* / physiology
  • Species Specificity

Grant support

Data collection, and associated costs in travel, consumables, and equipment, was supported by the Field Museum of Natural History Council on Africa (, the University of Chicago Hinds Fund (, and grants-in-aid of research from the American Society of Mammalogists (, Sigma Xi (, and the Society for Integrative & Comparative Biology ( During this study, B.M.K. was supported by a Predoctoral Fellowship (NSF GRFP ID #: 2006041573) from the National Science Foundation ( The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.