title: Preferred gait and walk-run transition speeds in ostriches measured using GPS-IMU sensors.
abstract: The ostrich (Struthio camelus) is widely appreciated as a fast and agile bipedal athlete, and is a useful comparative bipedal model for human locomotion. Here, we used GPS-IMU sensors to measure naturally selected gait dynamics of ostriches roaming freely over a wide range of speeds in an open field and developed a quantitative method for distinguishing walking and running using accelerometry. We compared freely selected gait-speed distributions with previous laboratory measures of gait dynamics and energetics. We also measured the walk-run and run-walk transition speeds and compared them with those reported for humans. We found that ostriches prefer to walk remarkably slowly, with a narrow walking speed distribution consistent with minimizing cost of transport (CoT) according to a rigid-legged walking model. The dimensionless speeds of the walk-run and run-walk transitions are slower than those observed in humans. Unlike humans, ostriches transition to a run well below the mechanical limit necessitating an aerial phase, as predicted by a compass-gait walking model. When running, ostriches use a broad speed distribution, consistent with previous observations that ostriches are relatively economical runners and have a flat curve for CoT against speed. In contrast, horses exhibit U-shaped curves for CoT against speed, with a narrow speed range within each gait for minimizing CoT. Overall, the gait dynamics of ostriches moving freely over natural terrain are consistent with previous lab-based measures of locomotion. Nonetheless, ostriches, like humans, exhibit a gait-transition hysteresis that is not explained by steady-state locomotor dynamics and energetics. Further study is required to understand the dynamics of gait transitions.
authors: Structure and Motion Lab, Royal Veterinary College, Hawkshead Lane, Hatfield AL97TA, UK mdaley@rvc.ac.uk.
authors: Monica A
authors: 0000-0001-8584-2052
authors: MA
authors: Daley
authors: Structure and Motion Lab, Royal Veterinary College, Hawkshead Lane, Hatfield AL97TA, UK.
authors: Anthony J
authors: AJ
authors: Channon
authors: Structure and Motion Lab, Royal Veterinary College, Hawkshead Lane, Hatfield AL97TA, UK.
authors: Grant S
authors: GS
authors: Nolan
authors: Structure and Motion Lab, Royal Veterinary College, Hawkshead Lane, Hatfield AL97TA, UK.
authors: Jade
authors: J
authors: Hall
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D005260:Female; D005684:Gait / Q000502:physiology*; D040362:Geographic Information Systems / Q000295:instrumentation*; D007700:Kinetics; D012420:Running / Q000502:physiology*; D020310:Struthioniformes / Q000502:physiology*; D016138:Walking / Q000502:physiology*
keywords: Biomechanics; Biped; Energetics; Gait transition; Locomotion; Struthio camelus