Mechanical and energetic scaling relationships of running gait through ontogeny in the ostrich (Struthio camelus)

Abstract

SUMMARYIt is unclear whether small animals, with their high stride frequency and crouched posture, or large animals, with more tendinous limbs, are more reliant on storage and return of elastic energy during locomotion. The ostrich has a limb structure that appears to be adapted for high-speed running with long tendons and short muscle fibres. Here we investigate biomechanics of ostrich gait through growth and, with consideration of anatomical data, identify scaling relationships with increasing body size, relating to forces acting on the musculoskeletal structures, effective mechanical advantage (EMA) and mechanical work. Kinematic and kinetic data were collected through growth from running ostriches. Joint moments scaled in a similar way to the pelvic limb segments as a result of consistent posture through growth, such that EMA was independent of body mass. Because no postural change was observed, relative loads applied to musculoskeletal tissues would be predicted to increase during growth, with greater muscle, and hence tendon, load allowing increased potential for elastic energy storage with increasing size. Mass-specific mechanical work per unit distance was independent of body mass, resulting in a small but significant increase in the contribution of elastic energy storage to locomotor economy in larger ostriches.

Preferred gait and walk–run transition speeds in ostriches measured using GPS-IMU sensors

“…While humans and ostriches have similar costs of walking for their body size, ostriches are relatively economical runners, whereas humans are relatively costly runners (Rubenson et al, 2007). Ostrich limb anatomy exhibits many specialized cursorial features, including elongated, fused and reduced distal elements and well-developed distal ligaments and tendons to enhance elastic energy cycling and allow high step frequencies to be achieved relatively cheaply (Smith et al, 2006;Schaller et al, 2009;Rubenson et al, 2011;Smith and Wilson, 2013). The slow transition to running and the broad distribution of self-selected running speeds exhibited by ostriches probably reflects their exceptionally well-specialized distal limb elasticity, thanks to a heritage of bipedal cursoriality extending back to theropod dinosaurs.…”

“…Gait dynamics and energetics have typically been measured at constant speeds on a treadmill (e.g. Hoyt and Taylor, 1981;Gatesy and Biewener, 1991;Rubenson et al, 2004;Watson et al, 2011;Smith and Wilson, 2013). Treadmills allow controlled measurement of steady gait at a speed determined by the experimenter.…”

“…Consequently, the ostrich has served as an important animal model for understanding bipedal gait dynamics and energetics (Fedak and Seeherman, 1979;Alexander et al, 1979;Abourachid and Renous, 2000;Rubenson et al, 2004;Smith et al, 2010;Watson et al, 2011;Smith and Wilson, 2013), and as an inspiration for the design of legged robots (Andrada et al, 2012;Cotton et al, 2012). Here, we measured self-selected gait dynamics of ostriches roaming in a 165×120 m grassy paddock over a wide range of speeds using GPS-IMU sensors, and compared freely selected gait-speed distributions with those reported previously from standard biomechanics laboratory measures.…”

Phalangeal joints kinematics during Ostrich (Struthio Camelus) locomotion

“…The 3rd toe sustains 105 most of the ground reaction force during locomotion and its claw provides the forces at 106 push-off in fast locomotion. While the 4th toe functions as a lateral support during 107 locomotion (Schaller et al, 2007(Schaller et al, , 2011 Although a large number of studies have been conducted to investigate the ostrich hindlimb 112 kinematics during locomotion (Haughton, 1865;Alexander et al, 1979;Alexander, 1985; 113 Gatesy and Biewener, 1991;Abourachid and Renous, 2000;Jindrich et al, 2007;Rubenson 114 et al, 2004Rubenson 114 et al, , 2007Rubenson 114 et al, , 2010Watson et al, 2011;Smith et al, 2006Smith et al, , 2007Smith et al, , 2010Smith et al, , 2013Schaller et 115 al., 2009Schaller et 115 al., , 2011Birn-Jeffery et al, 2014;Hutchinson et al, 2015), those kinematic analyses 116 were mainly focused on hip, knee and ankle joints. So far, little is known about the relative 117 motions of the 3rd and 4th toes intrinsic joints and the metatarsophalangeal joint during 118 ostrich foot locomotion.…”

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“…All the other birds 99 have three or four toes, while the largest avian biped ostrich has only two toes, the main 3rd 100 toe and the lateral 4th toe. Another unique adaptation at the distal part of the hindlimb is the 101 supra-jointed toe posture with the metatarsophalangeal joint and proximal phalanx of both 102 toes being permanently elevated above the ground surface (Schaller, et al, 2011;Deeming, 103 2003 (Schaller et al, 2007(Schaller et al, , 2011 Although a large number of studies have been conducted to investigate the ostrich hindlimb 112 kinematics during locomotion (Haughton, 1865;Alexander et al, 1979;Alexander, 1985;113 Gatesy and Biewener, 1991;Abourachid and Renous, 2000;Jindrich et al, 2007;Rubenson 114 et al, 2004Rubenson 114 et al, , 2007Rubenson 114 et al, , 2010Watson et al, 2011;Smith et al, 2006Smith et al, , 2007Smith et al, , 2010Smith et al, , 2013Schaller et 115 al., 2009Schaller et 115 al., , 2011Birn-Jeffery et al, 2014;Hutchinson et al, 2015), those kinematic analyses 116 were mainly focused on hip, knee and ankle joints. So far, little is known about the relative 117 motions of the 3rd and 4th toes intrinsic joints and the metatarsophalangeal joint during 118 ostrich foot locomotion.…”