Gait
Gait is the pattern of movement of the limbs of animals, including humans, during locomotion over a solid substrate. Most animals use a variety of gaits, selecting gait based on speed, terrain, the need to maneuver, and energetic efficiency. Different animal species may use different gaits due to differences in anatomy that prevent use of certain gaits, or simply due to evolved innate preferences as a result of habitat differences. While various gaits are given specific names, the complexity of biological systems and interacting with the environment make these distinctions 'fuzzy' at best. Gaits are typically classified according to footfall patterns, but recent studies often prefer definitions based on mechanics. The term typically does not refer to limb-based propulsion through fluid mediums such as water or air, but rather to propulsion across a solid substrate by generating reactive forces against it (which can apply to walking while underwater as well as on land). Due to the rapidity of animal movement, simple direct observation is rarely sufficient to give any insight into the pattern of limb movement. In spite of early attempts to classify gaits based on footprints or the sound of footfalls, it was not until Eadweard Muybridge and Étienne-Jules Marey
Étienne-Jules Marey began taking rapid series of photographs that proper scientific examination of gaits could begin.

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Contents

1 Overview 2 Variables 3 Physiological effects of gait 4 Differences between species 5 Energy-based gait classification 6 Energetics 7 Non-tetrapod gaits 8 See also 9 References

Overview[edit] Milton Hildebrand pioneered the contemporary scientific analysis and the classification of gaits. The movement of each limb was partitioned into a stance phase, where the foot was in contact with the ground, and a swing phase, where the foot was lifted and moved forwards.[1] Each limb must complete a cycle in the same length of time, otherwise one limb's relationship to the others can change with time, and a steady pattern cannot occur. Thus, any gait can completely be described in terms of the beginning and end of stance phase of three limbs relative to a cycle of a reference limb, usually the left hindlimb. Variables[edit]

Gait
Gait graphs in the style of Hildebrand. Dark areas indicate times of contact, bottom axis is % of cycle

Gaits are generally classed as "symmetrical" and "asymmetrical" based on limb movement. It is important to note that these terms have nothing to do with left-right symmetry. In a symmetrical gait, the left and right limbs of a pair alternate, while in an asymmetrical gait, the limbs move together. Asymmetrical gaits are sometimes termed "leaping gaits", due to the presence of a suspended phase. The key variables for gait are the duty factor and the forelimb-hindlimb phase relationship. Duty factor is simply the percent of the total cycle which a given foot is on the ground. This value will usually be the same for forelimbs and hindlimbs unless the animal is moving with a specially trained gait or is accelerating or decelerating. Duty factors over 50% are considered a "walk", while those less than 50% are considered a run. Forelimb-hindlimb phase is the temporal relationship between the limb pairs. If the same-side forelimbs and hindlimbs initiate stance phase at the same time, the phase is 0 (or 100%). If the same-side forelimb contacts the ground half of the cycle later than the hindlimb, the phase is 50%. Physiological effects of gait[edit] Gait
Gait choice can have effects beyond immediate changes in limb movement and speed, notably in terms of ventilation. Because they lack a diaphragm, lizards and salamanders must expand and contract their body wall in order to force air in and out of their lungs, but these are the same muscles used to laterally undulate the body during locomotion. Thus, they cannot move and breathe at the same time, a situation called Carrier's constraint, though some, such as monitor lizards, can circumvent this restriction via buccal pumping. In contrast, the spinal flexion of a galloping mammal causes the abdominal viscera to act as a piston, inflating and deflating the lungs as the animal's spine flexes and extends, increasing ventilation and allowing greater oxygen exchange. Differences between species[edit]

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A hamster walking on a transparent treadmill.

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Alternating tripod gait of walking desert ants.

Any given animal uses a relatively restricted set of gaits, and different species use different gaits. Almost all animals are capable of symmetrical gaits, while asymmetrical gaits are largely confined to mammals, who are capable of enough spinal flexion to increase stride length (though small crocodilians are capable of using a bounding gait). Lateral sequence gaits during walking and running are most common in mammals,[2] but arboreal mammals such as monkeys, some opossums, and kinkajous use diagonal sequence walks for enhanced stability.[2] Diagonal sequence walks and runs (aka trots) are most frequently used by sprawling tetrapods such as salamanders and lizards, due to the lateral oscillations of their bodies during movement. Bipeds
Bipeds are a unique case, and most bipeds will display only three gaits - walking, running, and hopping - during natural locomotion. Other gaits, such as human skipping, are not used without deliberate effort. Energy-based gait classification[edit] While gaits can be classified by footfall, new work involving whole-body kinematics and force-plate records has given rise to an alternative classification scheme, based on the mechanics of the movement. In this scheme, movements are divided into walking and running. Walking
Walking gaits are all characterized by a 'vaulting' movement of the body over the legs, frequently described as an inverted pendulum (displaying fluctuations in kinetic and potential energy which are perfectly out of phase). In running, the kinetic and potential energy fluctuate in-phase, and the energy change is passed on to muscles, bones, tendons and ligaments acting as springs (thus it is described by the spring-mass model). Energetics[edit]

Bison galloping

Speed generally governs gait selection, with quadrupedal mammals moving from a walk to a run to a gallop as speed increases. Each of these gaits has an optimum speed, at which the minimum calories per meter are consumed, and costs increase at slower or faster speeds. Gait
Gait transitions occur near the speed where the cost of a fast walk becomes higher than the cost of a slow run. Unrestrained animals will typically move at the optimum speed for their gait to minimize energy cost. The cost of transport is used to compare the energetics of different gaits, as well as the gaits of different animals. Non-tetrapod gaits[edit] In spite of the differences in leg number shown in terrestrial vertebrates, according to the inverted pendulum model of walking and spring-mass model of running, "walks" and "runs" are seen in animals with 2, 4, 6, or more legs. The term 'gait' has even been applied to flying and swimming organisms that produce distinct patterns of wake vortices. See also[edit]

Bipedal gait cycle Gait
Gait analysis Gait
Gait abnormality Gait
Gait (dog) Gait
Gait (human) Horse gait Parkinsonian gait

References[edit]

^ Tasch, U.; Moubarak, P.; Tang, W.; Zhu, L.; Lovering, R. M.; Roche, J.; Bloch, R. J. (2008). "An Instrument That Simultaneously Measures Spatiotemporal Gait
Gait Parameters and Ground Reaction Forces of Locomoting Rats": 45–49. doi:10.1115/ESDA2008-59085.  ^ a b Lemelin P, Schmitt D and Cartmill M. 2003. Footfall patterns and interlimb co-ordination in opossums (Family Didelphidae): evidence for the evolution of diagonal-sequence walking gaits in primates. J. Zool. Lond. 260:423-429. Web link to pdf

This article includes a list of references, but its sources remain unclear because it has insufficient inline citations. Please help to improve this article by introducing more precise citations. (August 2009) (Learn how and when to remove this template message)

Hildebrand, M. (1989). " Vertebrate
Vertebrate locomotion an introduction how does an animal's body move itself along?". BioScience. 39 (39): 764–765. doi:10.1093/bioscience/39.11.764. JSTOR 1311182.  Hoyt, D. F.; Taylor, R. C. (1981). " Gait
Gait and the energetics of locomotion in horses". Nature. 292 (292): 239–240. doi:10.1038/292239a0.  Carrier, D. (1987). "Lung ventilation during walking and running in four species of lizards". Experimental Biology. 47 (1): 33–42. PMID 3666097.  Bramble, D. M.; Carrier, D. R (1983). " Running
Running and breathing in mammals". Science. 219 (4582): 251–256. doi:10.1126/science.6849136. PMID 6849136.  Blickhan, R.; Full, R. J. (1993). "Similarity in multilegged locomotion: Bouncing like a monopode". Journal of Comparative Physiology A. 173: 509–517. doi:10.1007/bf00197760.  Cavagna, G. A.; Heglund, N. C.; Taylor, R. C. (1977). "Mechanical work in terrestrial locomotion: two basic mechanisms for minimizing energy expenditure". Am. J. Physiol. 233 (5): R243–R261. PMID 411381. 

v t e

Animal locomotion
Animal locomotion on land

Gait
Gait class

Legged

Arboreal
Arboreal locomotion (Brachiation) Hand-walking Jumping Knuckle-walking Running Walking

Legless

Concertina movement Undulatory locomotion Rectilinear locomotion Rolling Sidewinding Other modes

Anatomy

Comparative foot morphology Arthropod leg Digitigrade Plantigrade Unguligrade Uniped Biped (Facultative) Triped Quadruped

Specific

Canine gait Horse gait Human gait

Animal locomotion
Animal locomotion on the surface layer of water Fish locomotion Volant animals

v t e

Fins, limbs and wings

Fins

Aquatic locomotion Cephalopod fin Fish locomotion Fin
Fin and flipper locomotion Caudal fin Dorsal fin Fish fin flipper Lobe-finned fish Ray-finned fish Pectoral fins Pelvic fin

Limbs

Limb development Limb morphology

digitigrade plantigrade unguligrade uniped biped facultative biped triped quadruped

Arthropod Cephalopod Tetrapod

dactyly

Digit

Wings

Flying and gliding animals Bat wing Bird wing

keel skeleton feathers

Insect wing Pterosaur wing Wingspan

Evolution

Evolution of fish Evolution of tetrapods Evolution of birds Origin of birds Origin of avian flight Evolution of cetaceans Comparative anatomy Convergent evolution Analogous structures Homologous structures

Related

Animal locomotion Gait Robot locomotion Samara Terrestrial locomotion Tradeoffs for locomotion in air and water Rotating locomotion Und