Limitations of animal running speed

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Cheetah chasing its prey. Captured at Ree Park - Ebeltoft Safari, Denmark. Photo by Malene Thyssen (http://commons.wikimedia.org/wiki/User:Malene) Gepardjagt1 (Acinonyx jubatus).jpg
Cheetah chasing its prey. Captured at Ree Park - Ebeltoft Safari, Denmark. Photo by Malene Thyssen (http://commons.wikimedia.org/wiki/User:Malene)

Limitations of animal running speed provides an overview of how various factors determine the maximum running speed. Some terrestrial animals are built for achieving extremely high speeds, such as the cheetah, pronghorn, race horse and greyhound, while humans can train to achieve high sprint speeds. There is no single determinant of maximum running speed: however, certain factors stand out against others and have been investigated in both animals and humans. These factors include: Muscle moment arms, foot morphology, muscle architecture, and muscle fiber type. Each factor contributes to the ground reaction force (GRF) and foot contact time of which the changes to increase maximal speed are not well understood across all species.

Contents

Ground reaction force and foot contact time

An example of torque in real life. Torque.JPG
An example of torque in real life.

Muscle moment arm

A muscle's moment arm is defined as the perpendicular distance from the muscle's line of action to the joint's center of rotation. As a general rule, the larger the moment arm of a muscle, the greater torque it can produce with the same amount of force. At the same time, the muscle would cause a smaller change in joint angle for the same amount of length change. As an example, holding a wrench at the very end of the handle (point B) makes it easier to loosen a bolt, however, requires your hand to travel a greater distance compared to holding the wrench closer to the bolt (point A). Although both the cheetah and greyhound are similar in size, the cheetah can attain speeds nearly twice as fast as the greyhound. This can be explained partly by the finding that moment arms of muscles at the knee and ankle joint in the cheetah are proportionally larger than those of the greyhound. [4] A similar comparison can be made between two similar species of lizards. It was found that geckoes more adapted for climbing have greater hip and shoulder retractor moment arms. Geckoes adapted for horizontal locomotion have greater knee and ankle extensor moment arms. [5]

Foot morphology

A lever in balance Lever Principle 3D.png
A lever in balance

Foot morphology in this context mainly refers to the ratio of forefoot (in front of the ankle joint) to the hindfoot (behind the ankle joint). This ratio is an indication of the effective mechanical advantage (EMA) and can also be represented by a balancing seesaw. A study done on humans, comparing ankle-foot structure using MRI, showed that sprinters had a longer forefoot:hindfoot ratio compared to non-sprinters. [6] This allows the foot to remain in contact with the ground for a longer amount of time while decreasing the moment arm. This decreases the rate of muscle shortening and increases the force generated by extensor muscles during the push off phase. [7] These larger gear ratios during the push off phase have been shown to occur in accelerating humans as well as top animal sprinters. [4] [6] [8] Larger moment arms of the cheetah may be achieved if the forefoot is also proportionally larger.

Muscle architecture and fiber type

Structure of a skeletal muscle Illu muscle structure.jpg
Structure of a skeletal muscle

Both the architecture and type of muscle play a crucial role in determining foot contact time and production of GRF. In humans, it has been shown that sprinters have longer muscle fascicle lengths and smaller pennation angles than non-sprinters. [9] [10] This contributes by increasing the muscle's shortening velocity. Other studies have shown that particular muscle fiber types are favored in sprinters versus non-sprinters, as well as within different levels of sprinters. Faster individuals tend to have a greater percentage of Type II (fast-twitch) muscle fibers. [11] [12] Higher percentage of fast-twitch muscle fibers lead to increased force production capability, as well as increased speed of contractions leading to shorter contact times.

Other

Other factors also play a role:

See also

Related Research Articles

<span class="mw-page-title-main">Running</span> Method of terrestrial locomotion allowing rapid movement on foot

Running is a method of terrestrial locomotion allowing humans and other animals to move rapidly on foot. Running is a type of gait characterized by an aerial phase in which all feet are above the ground. This is in contrast to walking, where one foot is always in contact with the ground, the legs are kept mostly straight and the center of gravity vaults over the stance leg or legs in an inverted pendulum fashion. A feature of a running body from the viewpoint of spring-mass mechanics is that changes in kinetic and potential energy within a stride co-occur, with energy storage accomplished by springy tendons and passive muscle elasticity. The term running can refer to any of a variety of speeds ranging from jogging to sprinting.

<span class="mw-page-title-main">Jumping</span> Form of movement in which an organism or mechanical system propels itself into the air

Jumping or leaping is a form of locomotion or movement in which an organism or non-living mechanical system propels itself through the air along a ballistic trajectory. Jumping can be distinguished from running, galloping and other gaits where the entire body is temporarily airborne, by the relatively long duration of the aerial phase and high angle of initial launch.

<span class="mw-page-title-main">Skeletal muscle</span> One of three major skeletal system types that connect to bones

Skeletal muscles are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscle tissue, and are often known as muscle fibers. The muscle tissue of a skeletal muscle is striated – having a striped appearance due to the arrangement of the sarcomeres.

A motor unit is made up of a motor neuron and all of the skeletal muscle fibers innervated by the neuron's axon terminals, including the neuromuscular junctions between the neuron and the fibres. Groups of motor units often work together as a motor pool to coordinate the contractions of a single muscle. The concept was proposed by Charles Scott Sherrington.

<span class="mw-page-title-main">Physical strength</span> Measure of a humans exertion of force on physical objects

Physical strength is the measure of a human's exertion of force on physical objects. Increasing physical strength is the goal of strength training.

<span class="mw-page-title-main">Gait (human)</span> A pattern of limb movements made during locomotion

A gait is a pattern of limb movements made during locomotion. Human gaits are the various ways in which humans can move, either naturally or as a result of specialized training. Human gait is defined as bipedal, biphasic forward propulsion of the center of gravity of the human body, in which there are alternate sinuous movements of different segments of the body with least expenditure of energy. Gait patterns are characterized by differences in limb movement patterns, overall velocity, forces, kinetic and potential energy cycles, and changes in contact with the ground.

<span class="mw-page-title-main">Plyometrics</span> Maximum-intensity explosive exercises

Plyometrics, also known as jump training or plyos, are exercises in which muscles exert maximum force in short intervals of time, with the goal of increasing power (speed-strength). This training focuses on learning to move from a muscle extension to a contraction in a rapid or "explosive" manner, such as in specialized repeated jumping. Plyometrics are primarily used by athletes, especially martial artists, sprinters and high jumpers, to improve performance, and are used in the fitness field to a much lesser degree.

Running economy (RE) measures runners' energy utilization when running at an aerobic intensity, and many physiological and biomechanical factors contribute to it. Oxygen consumption (VO2) is the most commonly used method for measuring running economy, as the exchange of gases in the body, specifically oxygen and carbon dioxide, closely reflects energy metabolism. Those who are able to consume less oxygen while running at a given velocity are said to have a better running economy. However, straightforward oxygen usage does not account for whether the body is metabolising lipids or carbohydrates, which produce different amounts of energy per unit of oxygen; as such, accurate measurements of running economy must use O2 and CO2 data to estimate the calorific content of the substrate that the oxygen is being used to respire.

<span class="mw-page-title-main">Footspeed</span> The maximum speed that a human can run

Footspeed, or sprint speed, is the maximum speed at which a human can run. It is affected by many factors, varies greatly throughout the population, and is important in athletics and many sports, such as association football, rugby football, American football, track and field, field hockey, baseball, and basketball.

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The giant cheetah is an extinct felid species that was closely related to the modern cheetah.

<span class="mw-page-title-main">Comparative foot morphology</span>

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<span class="mw-page-title-main">Locomotor effects of shoes</span>

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<span class="mw-page-title-main">Architectural gear ratio</span> Ratio between muscle-shortening velocity and fiber-shortening velocity

Architectural gear ratio, also called anatomical gear ratio (AGR) is a feature of pennate muscle defined by the ratio between the longitudinal strain of the muscle and muscle fiber strain. It is sometimes also defined as the ratio between muscle-shortening velocity and fiber-shortening velocity.

<span class="mw-page-title-main">Biomechanics of sprint running</span>

Sprinting involves a quick acceleration phase followed by a velocity maintenance phase. During the initial stage of sprinting, the runners have their upper body tilted forward in order to direct ground reaction forces more horizontally. As they reach their maximum velocity, the torso straightens out into an upright position. The goal of sprinting is to reach and maintain high top speeds to cover a set distance in the shortest possible time. A lot of research has been invested in quantifying the biological factors and mathematics that govern sprinting. In order to achieve these high velocities, it has been found that sprinters have to apply a large amount of force onto the ground to achieve the desired acceleration, rather than taking more rapid steps.

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Terrestrial locomotion by means of a running gait can be accomplished on level surfaces. However, in most outdoor environments an individual will experience terrain undulations requiring uphill running. Similar conditions can be mimicked in a controlled environment on a treadmill also. Additionally, running on inclines is used by runners, both distance and sprinter, to improve cardiovascular conditioning and lower limb strength.

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