Toe function and dynamic pressure distribution in ostrich locomotion

Abstract

SUMMARYThe ostrich is highly specialized in terrestrial locomotion and is the only extant bird that is both didactyl and exhibits a permanently elevated metatarsophalangeal joint. This extreme degree of digitigrady provides an excellent opportunity for the study of phalangeal adaptation towards fast, sustained bipedal locomotion. Data were gathered in a semi-natural setting with hand-raised, cooperative specimens. Dynamic pressure distribution, centre of pressure (CoP) trajectory and the positional interrelationship of the toes during stance phase were investigated using pedobarography. Walking and running trials shared a Jshaped CoP trajectory with greater localization of CoP origin as speed increased. Slight variations of 4th toe position in walking affect CoP origin and modulation of 4th toe pressure on the substrate allows correction of balance, primarily at the beginning of stance phase at lower speeds. Load distribution patterns differed significantly between slow and fast trials. In walking, the 3rd and particularly the 4th toe exhibited notable variation in load distribution with minor claw participation only at push-off. Running trials yielded a distinctly triangular load distribution pattern defined by the 4th toe tip, the proximal part of the 3rd toe and the claw tip, with the sharp point of the claw providing an essential traction element at push-off. Consistency of CoP trajectory and load distribution at higher speeds arises from dynamic stability effects and may also reflect stringent limitations to degrees of freedom in hindlimb joint articulation that contribute to locomotor efficiency. This novel research could aid in the reconstruction of theropod locomotor modes and offers a systemic approach for future avian pedobarographic investigations.

Phalangeal joints kinematics during Ostrich (Struthio Camelus) locomotion

“…Rough skins, sturdy ligaments, fascia and lumpy fat pads envelop the metatarsophalangeal joints, toe skeleton and interphalangeal joints to ensure structural integrity, seemingly providing limitation on toe mobility (Schaller et al, 2011). However, our study reveal that almost all the six major toe joints present notably large motions from slow to fast locomotion.…”

“…The 3rd toe and claw essentially forming an extension of the tarsometatarsal limb sustain most of the impact force at touch-down and ensure stable load bearing and grip during stance phase (Schaller et al, 2011). During walking and running, just after touch-down, simultaneous flexions at the first phalangeal joint of the 3rd toe and the MTP3 joint, and also an extension at the second phalangeal joint of the 3rd toe occurs implying compliance at the interphalangeal joints of the 3rd toe is used to moderate ground impact at touch-down.…”

“…USA). In this study, trials with stance duration > 0.9s and duty factor > 0.5 were considered 244 as walking gaits, whereas trials with stance duration < 0.9s and duty factor < 0.5 were regarded as running gaits (Schaller et al, 2011 (Schache, 2011;Stoessel and Fischer, 2012 From Figure 4C and D, we can see that the angle  showed similar patterns in the stance 287 phases of walking and running. The joint angle decreased after touch-down from about 160 288 degree to 120 degree or so at late stance.…”

“…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 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, locomotion with different load distributions in walking and running. 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.…”

“…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.…”