Gait - AbsoluteAstronomy.com

This is an article on gaits of all animals; for other meanings, see: Gait (disambiguation)
Gait (disambiguation)
Gait may refer to:Movement*Gait, the pattern of limb movement during locomotion*Gait , locomotion achieved using human limbs*Gait , quality of movement, important in assessing breeds*Horse gait, types of horse movementTechnology...

.

Gait is the pattern of movement

Motion (physics)

In physics, motion is a change in position of an object with respect to time. Change in action is the result of an unbalanced force. Motion is typically described in terms of velocity, acceleration, displacement and time . An object's velocity cannot change unless it is acted upon by a force, as...

of the limb

Limb (anatomy)

A limb is a jointed, or prehensile , appendage of the human or other animal body....

s of animals, including humans

Gait (human)

Human gait is the way locomotion is achieved using human limbs. Different gaits are characterized by differences in limb movement patterns, overall velocity, forces, kinetic and potential energy cycles, and changes in the contact with the surface .- Foot strike :One variable in different gaits is...

, during locomotion over a solid substrate. Most animals use a variety of gaits, selecting gait based on speed

Speed

In kinematics, the speed of an object is the magnitude of its velocity ; it is thus a scalar quantity. The average speed of an object in an interval of time is the distance traveled by the object divided by the duration of the interval; the instantaneous speed is the limit of the average speed as...

, terrain

Terrain

Terrain, or land relief, is the vertical and horizontal dimension of land surface. When relief is described underwater, the term bathymetry is used...

, the need to maneuver

Maneuver

Maneuver, manoeuvre may be a synonym for strategy or tactic. It is the manipulation of a situation in order to gain some advantage.- Military or naval movement :* Military exercise...

, and energetic efficiency. Different animal species may use different gaits due to differences in anatomy

Anatomy

Anatomy is a branch of biology and medicine that is the consideration of the structure of living things. It is a general term that includes human anatomy, animal anatomy , and plant 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

Footfall

Footfall is a 1985 science fiction novel written by Larry Niven and Jerry Pournelle. It was nominated for the both the Hugo and Locus Awards in 1986, and was a No...

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 wasn't until Eadweard Muybridge

Eadweard Muybridge

Eadweard J. Muybridge was an English photographer who spent much of his life in the United States. He is known for his pioneering work on animal locomotion which used multiple cameras to capture motion, and his zoopraxiscope, a device for projecting motion pictures that pre-dated the flexible...

and Étienne-Jules Marey

Étienne-Jules Marey

Étienne-Jules Marey was a French scientist and chronophotographer.His work was significant in the development of cardiology, physical instrumentation, aviation, cinematography and the science of labor photography...

began taking rapid series of photographs that proper scientific examination of gaits could begin.

Overview

Milton Hildebrand pioneered the scientific analysis and classification

Medical classification

Medical classification, or medical coding, is the process of transforming descriptions of medical diagnoses and procedures into universal medical code numbers...

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 hindlimb.

Variables

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

Left-right symmetry

Left–right symmetry is a general principle in physics which holds that valid physical laws must not produce a different result for a motion that is left-handed than motion that is right-handed...

. 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

Forelimb

A forelimb is an anterior limb on an animal's body. When referring to quadrupeds , the term foreleg is often instead used....

-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

Acceleration

In physics, acceleration is the rate of change of velocity with time. In one dimension, acceleration is the rate at which something speeds up or slows down. However, since velocity is a vector, acceleration describes the rate of change of both the magnitude and the direction of velocity. ...

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

Time

Time is a part of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify rates of change such as the motions of objects....

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%.

Differences between species

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 mammal

Mammal

Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

s, who are capable of enough spinal

Vertebral column

In human anatomy, the vertebral column is a column usually consisting of 24 articulating vertebrae, and 9 fused vertebrae in the sacrum and the coccyx. It is situated in the dorsal aspect of the torso, separated by intervertebral discs...

flexion to increase stride length (though small crocodilia

Crocodilia

Crocodilia is an order of large reptiles that appeared about 84 million years ago in the late Cretaceous Period . They are the closest living relatives of birds, as the two groups are the only known survivors of the Archosauria...

ns are capable of using a bounding gait). Lateral sequence gaits

Ambling

The term amble or ambling is used to describe a number of four-beat intermediate gaits of horses. All are faster than a walk but usually slower than a canter or gallop...

during walking and running are most common in mammals, but arboreal mammals such as monkey

Monkey

A monkey is a primate, either an Old World monkey or a New World monkey. There are about 260 known living species of monkey. Many are arboreal, although there are species that live primarily on the ground, such as baboons. Monkeys are generally considered to be intelligent. Unlike apes, monkeys...

s, some possum

Possum

A possum is any of about 70 small to medium-sized arboreal marsupial species native to Australia, New Guinea, and Sulawesi .Possums are quadrupedal diprotodont marsupials with long tails...

s, and kinkajou

Kinkajou

The kinkajou , also known as the honey bear , is a rainforest mammal of the family Procyonidae related to olingos, coatis, raccoons, and the ringtail and cacomistle. It is the only member of the genus Potos. Kinkajous may be mistaken for ferrets or monkeys, but are not closely related...

s use diagonal sequence walks for enhanced stability. Diagonal sequence walks and runs (aka trots) are most frequently used by sprawling tetrapod

Tetrapod

Tetrapods are vertebrate animals having four limbs. Amphibians, reptiles, birds and mammals are all tetrapods; even snakes and other limbless reptiles and amphibians are tetrapods by descent. The earliest tetrapods evolved from the lobe-finned fishes in the Devonian...

s such as salamander

Salamander

Salamander is a common name of approximately 500 species of amphibians. They are typically characterized by a superficially lizard-like appearance, with their slender bodies, short noses, and long tails. All known fossils and extinct species fall under the order Caudata, while sometimes the extant...

s and lizard

Lizard

Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...

s, due to the lateral oscillations of their bodies during movement. 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.

Physiological effects of gait

Gait choice can have effects beyond immediate changes in limb movement and speed, notably in terms of ventilation

Ventilation (physiology)

In respiratory physiology, ventilation is the rate at which gas enters or leaves the lung. It is categorized under the following definitions:-Sample values:...

. Because they lack a diaphragm

Thoracic diaphragm

In the anatomy of mammals, the thoracic diaphragm, or simply the diaphragm , is a sheet of internal skeletal muscle that extends across the bottom of the rib cage. The diaphragm separates the thoracic cavity from the abdominal cavity and performs an important function in respiration...

, 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

Carrier's constraint

Carrier's constraint is the observation that air-breathing vertebrates which have two lungs and flex their bodies sideways during locomotion find it very difficult to move and breathe at the same time, because:...

, though some, such as monitor lizards, can circumvent this restriction via buccal pumping

Buccal pumping

Buccal pumping is a method of respiration in which the animal moves the floor of the mouth in a rhythmic manner that is externally apparent.This method has several stages. These will be described for an animal starting with lungs in a deflated state: First, the glottis is closed, and the...

. 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

Breathing

Breathing is the process that moves air in and out of the lungs. Aerobic organisms require oxygen to release energy via respiration, in the form of the metabolism of energy-rich molecules such as glucose. Breathing is only one process that delivers oxygen to where it is needed in the body and...

Energy-based gait classification

While gaits can be classified by footfall

Footfall

Footfall is a 1985 science fiction novel written by Larry Niven and Jerry Pournelle. It was nominated for the both the Hugo and Locus Awards in 1986, and was a No...

, new work involving whole-body kinematics

Kinematics

Kinematics is the branch of classical mechanics that describes the motion of bodies and systems without consideration of the forces that cause the motion....

and force-plate records has given rise to an alternative classification scheme, based on the mechanics of the movement

Motion (physics)

. In this scheme, movements are divided into walking and running. Walking gaits are all characterized by a 'vaulting' movement of the body over the legs, frequently described as in inverted pendulum (displaying fluctuations in kinetic and potential energy

Potential energy

In physics, potential energy is the energy stored in a body or in a system due to its position in a force field or due to its configuration. The SI unit of measure for energy and work is the Joule...

which are perfectly out of phase). In running, the kinetic and potential energy fluctuate in-phase, and the energy change is passed on to muscle

Muscle

Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...

s, bone

Bone

Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...

s, tendon

Tendon

A tendon is a tough band of fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension. Tendons are similar to ligaments and fasciae as they are all made of collagen except that ligaments join one bone to another bone, and fasciae connect muscles to other...

s and ligament

Ligament

In anatomy, the term ligament is used to denote any of three types of structures. Most commonly, it refers to fibrous tissue that connects bones to other bones and is also known as articular ligament, articular larua, fibrous ligament, or true ligament.Ligament can also refer to:* Peritoneal...

s acting as springs (thus it is described by the spring-mass model).

Energetics

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 at 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.

Non-tetrapod gaits

In spite of the differences in leg number shown in terrestrial

Terrestrial animal

Terrestrial animals are animals that live predominantly or entirely on land , as compared with aquatic animals, which live predominantly or entirely in the water , or amphibians, which rely on a combination of aquatic and terrestrial habitats...

vertebrate

Vertebrate

Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...

s, according to the inverted pendulum

Inverted pendulum

An inverted pendulum is a pendulum which has its mass above its pivot point. It is often implemented with the pivot point mounted on a cart that can move horizontally and may be called a cart and pole...

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 who produce distinct patterns of wake vortices.