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
Étienne-Jules Marey began taking rapid series of
photographs that proper scientific examination of gaits could begin.
Look up gait in Wiktionary, the free dictionary.
3 Physiological effects of gait
4 Differences between species
5 Energy-based gait classification
7 Non-tetrapod gaits
8 See also
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.
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
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
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
A hamster walking on a transparent treadmill.
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, but arboreal mammals such as monkeys, some
opossums, and kinkajous use diagonal sequence walks for enhanced
stability. 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
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
Energy-based gait classification
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
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).
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 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.
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
Bipedal gait cycle
^ Tasch, U.; Moubarak, P.; Tang, W.; Zhu, L.; Lovering, R. M.; Roche,
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Gait Parameters and Ground Reaction Forces of
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^ 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
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2009) (Learn how and when to remove this template message)
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Animal locomotion on land
Arboreal locomotion (Brachiation)
Comparative foot morphology
Animal locomotion on the surface layer of water
Fins, limbs and wings
Fin and flipper locomotion
Flying and gliding animals
Evolution of fish
Evolution of tetrapods
Evolution of birds
Origin of birds
Origin of avian flight
Evolution of cetaceans
Tradeoffs for locomotion in air and water