Gait is the pattern of movement In physics, motion is change of location or position of an object with respect to time. Change in motion is the result of an applied force. Motion is typically described in terms of velocity also seen as speed, acceleration, displacement, and time. An object's velocity cannot change unless it is acted upon by a force, as described by Newton's of the limbs of animals, including humans 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, during locomotion over a solid substrate. Most animals use a variety of gaits, selecting gait based on speed In kinematics, the instantaneous speed of an object is the magnitude of its instantaneous velocity (the rate of change of its position); it is thus the scalar equivalent of velocity. 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, terrain Terrain, or land relief, is the vertical dimension of land surface. When relief is described underwater, the term bathymetry is used. Topography has recently become an additional synonym, though in many parts of the world it retains its original more general meaning of description of place, the need to maneuver, and energetic efficiency. Different animal species may use different gaits due to differences in 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 (zootomy) and plant anatomy (phytotomy). In some of its facets anatomy is closely related to embryology, comparative anatomy and comparative embryology, through common roots in 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 wasn't until Eadweard Muybridge Eadweard J. Muybridge was an English photographer, known primarily for his important pioneering work on animal locomotion, with use of multiple cameras to capture motion, and his zoopraxiscope, a device for projecting motion pictures that pre-dated the flexible perforated film strip that is used today and Étienne-Jules Marey Étienne-Jules Marey was a French scientist and chronophotographer 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, or medical coding, is the process of transforming descriptions of medical diagnoses and procedures into universal medical code numbers. The diagnoses and procedures are usually taken from a variety of sources within the medical record, such as the transcription of the doctor's notes, laboratory results, radiologic results, 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 Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency. The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency, 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. 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 A forelimb is an anterior limb (arm, leg, or similar appendage) on an animal's body. When referring to quadrupeds (four-legged animals), 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 In physics, and more specifically kinematics, acceleration is the change in velocity over time. Because velocity is a vector, it can change in two ways: a change in magnitude and/or a change in direction. In one dimension, i.e. a line, acceleration is the rate at which something speeds up. However, as a vector quantity, acceleration is also the 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 is "a nonspatial continuum in which events occur in apparently irreversible succession from the past through the present to the future." It is used to sequence events, to quantify the durations of events and the intervals between them, and to quantify and measure the motions of objects and other changes. Time is quantified in 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 mammals Mammals are a class of vertebrate, air-breathing animals whose females are characterized by the possession of mammary glands while both males and females are characterized by hair and/or fur, three middle ear bones used in hearing, and a neocortex region in the brain. Some mammals have sweat glands, but most do not, who are capable of enough spinal flexion to increase stride length (though small crocodilians Crocodilia is an order of large reptiles that appeared about 84 million years ago in the late Cretaceous Period (Campanian stage). They are the closest living relatives of birds, as the two groups are the only known survivors of the Archosauria. Members of the crocodilian stem group, the clade Crurotarsi, appeared about 220 million years ago in are capable of using a bounding gait). Lateral sequence gaits 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. They are smoother for a rider than either the two-beat trot or pace and most can be sustained for relatively long periods of time, making them particularly desirable for trail during walking and running are most common in mammals, but arboreal Arboreal locomotion is the locomotion of animals in trees. In every habitat in which trees are present, animals have evolved to move in them. Some animals may only scale trees occasionally, while others are exclusively arboreal. These habitats pose numerous mechanical challenges to animals moving through them, leading to a variety of anatomical, mammals such as monkeys A monkey is any cercopithecoid or platyrrhine (New World monkey) primate. All primates that are not prosimians (lemurs and tarsiers) or apes are monkeys. The 264 known extant monkey species represent two of the three groupings of simian primates (the third group being the 21 species of apes). Monkeys are generally considered to be intelligent and,, some possums A possum is any of about 69 small to medium-sized arboreal marsupial species native to Australia, New Guinea, and Sulawesi (and introduced to New Zealand and China). The name derives from their resemblance to the opossums of the Americas. The term "possum" is also used in North America as a short form of "Opossum", although, and kinkajous The kinkajou , also known as the honey bear (a name it shares with the sun 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 related. Native to Central America and use diagonal sequence walks for enhanced stability. Diagonal sequence walks and runs (aka trots) are most frequently used by sprawling tetrapods Tetrapods are vertebrate animals having four feet, legs or leglike appendages. Amphibians, reptiles, dinosaurs, birds, and mammals are all tetrapods, and even the limbless snakes are tetrapods by descent. The earliest tetrapods radiated from the Sarcopterygii, or lobe-finned fish such as salamanders Salamander is a common name of approximately 500 species of amphibians. They are typically characterized by their slender bodies, short noses, and long tails. All known fossils and extinct species fall under the order Caudata, while sometimes the extant species are grouped together as the Urodela. Most salamanders have four toes on their front and lizards Lizards are a very large and widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains. The group, traditionally recognized as the suborder Lacertilia, is defined as all extant members of the Lepidosauria , which are neither sphenodonts (i.e., tuatara) nor, 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 In respiratory physiology, ventilation is the rate at which gas enters or leaves the lung. It is categorised under the following definitions:. Because they lack a diaphragm In the anatomy of mammals, the thoracic diaphragm or sometime simply, the diaphragm, is a sheet of internal 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. A diaphragm in anatomy can refer to other flat structures such as, 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 Monitor lizards increase their stamina by using bones and muscles in the throat and floor of the mouth to "gulp" air via buccal pumping, 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 In anatomy, a viscus is an internal organ, and viscera is the plural form. The viscera, when removed from a butchered animal, are known collectively as offal. Internal organs are also known as "innards", or less formally, "guts" (which may also refer to the gastrointestinal tract) 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 is the process that takes oxygen in and carbon dioxide in and then out of the body. Aerobic organisms require oxygen to release energy via respiration, in the form of the metabolism of energy-rich molecules such as glucose. The medical term for normal relaxed breathing is eupnea.

Energy-based gait classification

While gaits can be classified by footfall, new work involving whole-body kinematics Kinematics is the branch of classical mechanics that describes the motion of objects without consideration of the causes leading to the motion and force-plate records has given rise to an alternative classification scheme, based on the mechanics of the movement In physics, motion is change of location or position of an object with respect to time. Change in motion is the result of an applied force. Motion is typically described in terms of velocity also seen as speed, acceleration, displacement, and time. An object's velocity cannot change unless it is acted upon by a force, as described by Newton's. In this scheme, movements are simply divided into simply 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 In physics, Potential energy is energy stored within a physical system as a result of the position or configuration of the different parts of that system. It has the potential to be converted into other forms of energy, such as kinetic energy, and to do work in the process. The SI unit of measure for energy and work is the joule (symbol J) 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 Muscle is the 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 produce force and cause motion. Muscles can cause, bones Bones are rigid organs that form part of the endoskeleton of vertebrates. They function to move, 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. Because bones come in a variety of shapes and have a complex internal and external structure, tendons 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 fascia as they are all made of collagen except that ligaments join one bone to another bone, and fascia connect muscles to other muscles. Tendons and muscles work together and can and ligaments The study of ligaments is known as desmology acting as springs (thus it is describes as the spring-mass model).

Energetics

Speed generally governs gait selection, with quadrupedal Quadrupedalism is a form of land animal locomotion using four limbs or legs. An animal or machine that usually moves in a quadrupedal manner is known as a quadruped, meaning "four feet" . The majority of walking animals are quadrupeds, including mammals such as cattle and cats, and reptiles, like lizards mammals general 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 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 (e.g., frogs). Terrestrial animals evolved from marine animals (aquatic animals living in the ocean). The vertebrates Vertebrates are members of the subphylum Vertebrata, chordates with backbones or spinal columns. About 58,000 species of vertebrates have been described. Vertebrata is the largest subphylum of chordates, and contains many familiar groups of large land animals. Vertebrates comprise cyclostomes, bony fish, sharks and rays, amphibians, reptiles,, according to the 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. Whereas a normal pendulum is stable when hanging downwards, an inverted pendulum is inherently unstable, and must be actively balanced in order to 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 A vortex is a spinning, often turbulent, flow of fluid. Any spiral motion with closed streamlines is vortex flow. The motion of the fluid swirling rapidly around a center is called a vortex. The speed and rate of rotation of the fluid in a free (irrotational) vortex are greatest at the center, and decrease progressively with distance from the.

See also

• Gait analysis Gait analysis is the systematic study of animal locomotion, using the eye and the brain of observers, augmented by instrumentation for measuring body movements, body mechanics and the activity of the muscles. Gait analysis is used to assess, plan and treate individuals with conditions affecting their ability to walk. It is also commonly used in
• 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
• Gait (dog) A dog's gait is its quality of movement. It is given a great deal of importance in the breed standard of some breeds, of lesser importance in other standards, and in some breeds gait is not described in the standard at all
• Horse gait Horse gaits are the various ways in which a horse can move, either naturally or as a result of specialized training by humans
• Parkinsonian Gait

References

• Hildebrand, M. (1989). "Vertebrate locomotion an introduction how does an animal's body move itself along?". Bioscience 39 (39): 764–765. http://www.jstor.org/pss/1311182.
• Hoyt, D. F.; Taylor, R. C. (1981). "Gait and the energetics of locomotion in horses". Nature 292 (292): 239–240. doi A digital object identifier is a character string used to uniquely identify an electronic document or other object. Metadata about the object is stored in association with the DOI name and this metadata may include a location, such as a URL, where the object can be found. The DOI for a document is permanent, whereas its location and other metadata:10.1038/292239a0. http://www.nature.com/nature/journal/v292/n5820/abs/292239a0.html.
• Carrier, D. (1987). "Lung ventilation during walking and running in four species of lizards". Experimental Biology (47): 33–42. http://www.ncbi.nlm.nih.gov/pubmed/3666097.
• Bramble, D. M.; Carrier, D. R (1983). "Running and breathing in mammals". Science 219 (219): 251–256. doi A digital object identifier is a character string used to uniquely identify an electronic document or other object. Metadata about the object is stored in association with the DOI name and this metadata may include a location, such as a URL, where the object can be found. The DOI for a document is permanent, whereas its location and other metadata:10.1126/science.6849136. PMID A PMID is a unique number assigned to each PubMed citation of life sciences and biomedical scientific journal articles. The related Pubmed Central archive may additionally assign a separate number, a PMCID (PubMed Central Identifier), normally written with a PMC prefix 6849136. http://www.sciencemag.org/cgi/content/abstract/sci;219/4582/251.
• Blickhan, R.; Full, R. J. (1993). "Similarity in multilegged locomotion: Bouncing like a monopode". Journal of Comparative Physiology A (173): 509–517. http://www.springerlink.com/content/k4n326302181t784/.
• 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 (233): R243–R261. PMID A PMID is a unique number assigned to each PubMed citation of life sciences and biomedical scientific journal articles. The related Pubmed Central archive may additionally assign a separate number, a PMCID (PubMed Central Identifier), normally written with a PMC prefix 411381. http://ajpregu.physiology.org/cgi/content/abstract/233/5/R243.

Categories: Locomotion | Human skills

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