Title
In search of the pitching momentum that enables some lizards to sustain bipedal running at constant speeds
Author
Faculty/Department
Faculty of Sciences. Biology
Publication type
article
Publication
London ,
Subject
Biology
Engineering sciences. Technology
Source (journal)
Journal of the Royal Society interface: physical and life sciences. - London
Volume/pages
10(2013) :84 , p. 1-8
ISSN
1742-5689
Article Reference
20130241
ISI
000319404300018
Carrier
E-only publicatie
Target language
English (eng)
Full text (Publishers DOI)
Affiliation
University of Antwerp
Abstract
The forelimbs of lizards are often lifted from the ground when they start sprinting. Previous research pointed out that this is a consequence of the propulsive forces from the hindlimbs. However, despite forward acceleration being hypothesized as necessary to lift the head, trunk and forelimbs, some species of agamids, teiids and basilisks sustain running in a bipedal posture at a constant speed for a relatively long time. Biomechanical modelling of steady bipedal running in the agamid Ctenophorus cristatus now shows that a combination of three mechanisms must be present to generate the angular impulse needed to cancel or oppose the effect of gravity. First, the trunk must be lifted significantly to displace the centre of mass more towards the hip joint. Second, the nose-up pitching moment resulting from aerodynamic forces exerted at the lizard's surface must be taken into account. Third, the vertical ground-reaction forces at the hindlimb must show a certain degree of temporal asymmetry with higher forces closer to the instant of initial foot contact. Such asymmetrical vertical ground-reaction force profiles, which differ from the classical spring-mass model of bipedal running, seem inherent to the windmilling, splayed-legged running style of lizards.
E-info
https://repository.uantwerpen.be/docman/iruaauth/2cd3a4/aefcacba25b.pdf
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