Data from: Preferred gait and walk-run transition speeds in ostriches measured using GPS-IMU sensors

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 use GPS-IMU sensors to measure naturally selected gait dynamics of ostriches roaming freely over a wide range of speeds in an open field and develop a quantitative method for distinguishing walking and running using accelerometry. We compare freely selected gait-speed distributions to previous laboratory measures of gait dynamics and energetics. We also measure the walk-to-run and run-to-walk transition speeds and compare to those reported for humans. We find 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-to-run and run-to-walk transitions are slower than 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 of running 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.