Transition from walking to running

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Human locomotion is considered to take two primary forms: walking and running. In contrast, many quadrupeds have three distinct forms of locomotion: walk, trot, and gallop. Walking is a form of locomotion defined by a double support phase when both feet are on the ground at the same time. Running is a form of locomotion that does not have this double support phase (switched into double float phase).

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Preferred transition speed

The preferred transition speed (PTS) is the speed at which an organism typically changes from one gait to another. Humans spontaneously switch from a walk to a run as speed increases. In humans, the preferred transition speed from walking to running typically occurs around 2.0 m/s (7.2 km/h; 4.5 mph), although slight differences have been shown based on testing methodology. [1] [2] [3] [4]

Why transition from walking to running at the PTS?

Humans are capable of walking at speeds faster than 2.0 m/s, and capable of running at speeds slower than 2.0 m/s. As humans can walk or run at the same pace, researchers have attempted to explain why humans choose the transition speed that they do.

Early researchers suggested that humans transition from walking to running in order to minimize energetic costs. [5] [6] [7] [8] These researchers suggested that the energetic cost to run above 2.0 m/s is lower than the cost of walking above this speed. Conversely, running at speeds slower than 2.0 m/s was suggested to be more costly than walking at these speeds.

This view was largely unchallenged until the late 1980s. Since that time, several studies have shown that transitioning from walking to running actually resulted in an increase in energy expenditure, while other studies have supported an energetic benefit from the transition. [9] [10] In the time since the energetics optimization view was first challenged, a number of mechanical, kinetic, and kinematic factors have been explored to explain the transition. Weak to moderately strong correlations have been found between several variables and the PTS, but work from a variety of researchers in the 1990s and 2000s agrees that ultimately it is fatigue and discomfort (or imminent fatigue/discomfort) in the tibialis anterior and other dorsiflexor muscles of the ankle that is the primary stimulus for the transition from walking to running in humans. [11] [12] [13]

Energetic factors

The energetics of movement are typically measured indirectly through oxygen consumption. Most of the energy for walking is produced through the combustion of nutrients in the presence of oxygen (as opposed to anaerobic or high-intensity exercise which relies increasingly on energy that does not require oxygen for breakdown). Oxygen consumption increases when transitioning from walking to running, despite Ratings of Perceived Exertion (RPE) decreasing. [9] Therefore, people feel that they are not working as hard by switching from walking to running, even though their energy expenditure has increased. Humans would have to transition to running at much faster speeds than 2.0 m/s (4.5 mph) in order for the transition to represent a decrease in energy consumption.[ citation needed ]

Mechanical factors

Across quadruped species, there is a strong correlation between body mass and the preferred transition speed from trotting to galloping. [6] However, in humans no single anthropometric factor explains the preferred transition speed to a similar degree. In humans the strongest correlations between anthropometric measurements and the PTS come from measurements related to leg length, with a weak correlation between PTS and body mass. [14] [2] In these studies, the strongest correlates came from measurements of total height and lower leg length.

Considering walking with the inverted pendulum model, one can predict maximum attainable walking speed with the Froude number, F = v^2 / lg, where v^2 = velocity squared, l = leg length, and g= gravity. The Froude number is a dimensionless value representing the ratio of Centripetal force to Gravitational force during walking. If the body is viewed as a mass moving through a circular arc centered over the foot, the theoretical maximum Froude number is 1.0, where centripetal and gravitational forces are equal. At a number greater than 1.0, the gravitational force would not be strong enough to hold the body in a horizontal plane and the foot would miss the ground. Humans make the transition from walking to running at a Froude number around 0.5. [13] [15] even under conditions simulating reduced gravity. [3]

Kinetic factors

Joint kinetic factors appear to be important in triggering trot-to-gallop transitions among quadrupeds. [16] [15] [17] Stress on bones, particularly at joints, is reduced after a transition in these animals; however the same did not occur during the walk-to-trot transition among these animals. The transition therefore may be triggered by different events across species and in the trot-to-gallop versus walk-to-trot transitions in these animals.[ citation needed ]

In humans, the PTS is believed by some to occur at critical levels of ankle dorsiflexor moments and power. [12] [18] Dorsiflexor muscles show high levels of activation when walking near the PTS and human subjects describe feeling fatigue in these muscles. [19] Ratings of Perceived Exertion (RPE) also decrease after the transition to running, despite a higher energetic expenditure.

The dorsiflexor muscles are small relative to other major muscles of the leg involved in locomotion such as the gluteals, hamstrings, quadriceps and the plantarflexors of the ankle. These muscles must exert large amounts of force at two points during the walking stride at high speeds: 1) The beginning of the stance phase of walking, when the heel touches down and the raised toes must be stabilized to avoid "slapping" the forefoot on the ground. 2) During the swing phase, the trailing leg is moved ahead of the foot planted on the ground and the toes must be raised to avoid colliding with the ground. Because of their relatively small size, these muscles are prone to fatigue quickly when asked to exert large amounts of force during high speed walking. The transition to running reduces the load on the dorsiflexor muscles and reduces the feeling of discomfort associated with fatigue of these muscles.[ citation needed ]

Related Research Articles

Walking Gait of locomotion among legged animals

Walking is one of the main gaits of terrestrial locomotion among legged animals. Walking is typically slower than running and other gaits. Walking is defined by an 'inverted pendulum' gait in which the body vaults over the stiff limb or limbs with each step. This applies regardless of the usable number of limbs—even arthropods, with six, eight, or more limbs, walk.

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.

Horse gait Ways of movement of equines

Horses can use various gaits during locomotion across solid ground, either naturally or as a result of specialized training by humans.

In continuum mechanics, the Froude number is a dimensionless number defined as the ratio of the flow inertia to the external field. Named after William Froude (;), the Froude number is based on the speed–length ratio which he defined as:

Gait analysis

Gait analysis is the systematic study of animal locomotion, more specifically the study of human motion, 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 and treat individuals with conditions affecting their ability to walk. It is also commonly used in sports biomechanics to help athletes run more efficiently and to identify posture-related or movement-related problems in people with injuries.

Brachiation Form of arboreal locomotion involving swinging by the arm

Brachiation, or arm swinging, is a form of arboreal locomotion in which primates swing from tree limb to tree limb using only their arms. During brachiation, the body is alternately supported under each forelimb. This form of locomotion is the primary means of locomotion for the small gibbons and siamangs of southeast Asia. Gibbons in particular use brachiation for as much as 80% of their locomotor activities. Some New World monkeys, such as spider monkeys and muriquis, were initially classified as semibrachiators and move through the trees with a combination of leaping and brachiation. Some New World species also practice suspensory behaviors by using their prehensile tail, which acts as a fifth grasping hand. Evidence has shown that the extinct ape Proconsul from the Milocene of East Africa developed an early form of suspensory behaviour, and was therefore referred to as a probrachiator.

Gait (human) Locomotion achieved through the movement of human limbs

A gait is a pattern of limb movements made during locomotion. Human gaits are the various ways in which a human 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. Different gait patterns are characterized by differences in limb-movement patterns, overall velocity, forces, kinetic and potential energy cycles, and changes in the contact with the ground.

Robot locomotion is the collective name for the various methods that robots use to transport themselves from place to place.

Ambling gait

An ambling gait or amble is any of several four-beat intermediate horse gaits, all of which are faster than a walk but usually slower than a canter and always slower than a gallop. Horses that amble are sometimes referred to as "gaited", particularly in the United States. Ambling gaits are smoother for a rider than either the two-beat trot or pace and most can be sustained for relatively long periods, making them particularly desirable for trail riding and other tasks where a rider must spend long periods in the saddle. Historically, horses able to amble were highly desired for riding long distances on poor roads. Once roads improved and carriage travel became popular, their use declined in Europe but continued in popularity in the Americas, particularly in areas where plantation agriculture was practiced and the inspection of fields and crops necessitated long daily rides.

Terrestrial locomotion

Terrestrial locomotion has evolved as animals adapted from aquatic to terrestrial environments. Locomotion on land raises different problems than that in water, with reduced friction being replaced by the increased effects of gravity.

A facultative biped is an animal that is capable of walking or running on two legs (bipedal), as a response to exceptional circumstances (facultative), while normally walking or running on four limbs or more. In contrast, obligate bipedalism is where walking or running on two legs is the primary method of locomotion. Facultative bipedalism has been observed in several families of lizards and multiple species of primates, including sifakas, capuchin monkeys, baboons, gibbons, gorillas, bonobos and chimpanzeess. Different facultatively bipedal species employ different types of bipedalism corresponding to the varying reasons they have for engaging in facultative bipedalism. In primates, bipedalism is often associated with food gathering and transport. In lizards, it has been debated whether bipedal locomotion is an advantage for speed and energy conservation or whether it is governed solely by the mechanics of the acceleration and lizard's center of mass. Facultative bipedalism is often divided into high-speed (lizards) and low-speed (gibbons), but some species cannot be easily categorized into one of these two. Facultative bipedalism has also been observed in cockroaches and some desert rodents.

The evolution of human bipedalism, which began in primates about four million years ago, or as early as seven million years ago with Sahelanthropus, or about 12 million years ago with Danuvius guggenmosi, has led to morphological alterations to the human skeleton including changes to the arrangement and size of the bones of the foot, hip size and shape, knee size, leg length, and the shape and orientation of the vertebral column. The evolutionary factors that produced these changes have been the subject of several theories.

The endurance running hypothesis is the hypothesis that the evolution of certain human characteristics can be explained as adaptations to long-distance running. The hypothesis suggests that endurance running played an important role for early hominins in obtaining food. Researchers have proposed that endurance running began as an adaptation for scavenging and later for persistence hunting.

Robert McNeill Alexander

Robert McNeill (Neill) Alexander, CBE FRS was a British zoologist and a leading authority in the field of biomechanics. Until 1970, he was mainly concerned with fish, investigating the mechanics of swim bladders, tails and fish jaw mechanisms. Subsequently, he concentrated on the mechanics of terrestrial locomotion, notably walking and running in mammals, particularly on gait selection and its relationship to anatomy and to the structural design of skeletons and muscles.

The preferred walking speed is the speed at which humans or animals choose to walk. Many people tend to walk at about 1.4 metres per second. Although many people are capable of walking at speeds upwards of 2.5 m/s, especially for short distances, they typically choose not to. Individuals find slower or faster speeds uncomfortable.

Obesity and walking describes how the locomotion of walking differs between an obese individual and a non-obese individual. The prevalence of obesity is becoming a worldwide problem, with the American population leading the way. In 2007-2008, prevalence rates for obesity among adult American men were approximately 32% and over 35% amongst adult American women. According to the Johns Hopkins Bloomberg School of Public Health, 66% of the American population is either overweight or obese and this number is predicted to increase to 75% by 2015. Obesity is linked to health problems such as decreased insulin sensitivity and diabetes, cardiovascular disease, cancer, sleep apnea, and joint pain such as osteoarthritis. It is thought that a major factor of obesity is that obese individuals are in a positive energy balance, meaning that they are consuming more calories than they are expending. Humans expend energy through their basal metabolic rate, the thermic effect of food, non-exercise activity thermogenesis (NEAT), and exercise. While many treatments for obesity are presented to the public, exercise in the form of walking is an easy, relatively safe activity that has the potential to move a person towards a negative energy balance and if done for a long enough time may reduce weight.

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.

Effect of gait parameters on energetic cost

The effect of gait parameters on energetic cost is a relationship that describes how changes in step length, cadence, step width, and step variability influence the mechanical work and metabolic cost involved in gait. The source of this relationship stems from the deviation of these gait parameters from metabolically optimal values, with the deviations due to environmental, pathological, and other factors.

Five-gaited

Five-gaited horses are notable for their ability to perform five distinct horse gaits instead of simply the three gaits, walk, trot and canter or gallop common to most horses. Individual animals with this ability are often seen in the American Saddlebred horse breed, though the Icelandic horse also has five-gaited individuals, though with a different set of gaits than the Saddlebred.

Locomotion in space

Locomotion in space includes any variety of actions or methods used to move one's body through an environment with microgravity conditions. Locomotion in these conditions is different from locomotion in Earth's gravity. There are many factors that contribute to these differences, and they are crucial when researching long-term survival of humans in space.

References

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  8. ↑ McMahon, TA (1985). "The role of compliance in mammalian running gaits". Journal of Experimental Biology. 115 (1): 263–82. PMID   4031769.
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  10. ↑ Sasaki, Kotaro; Neptune, Richard R. (April 2006). "Muscle mechanical work and elastic energy utilization during walking and running near the preferred gait transition speed". Gait & Posture. 23 (3): 383–390. doi:10.1016/j.gaitpost.2005.05.002. ISSN   0966-6362. PMID   16029949.
  11. ↑ Prilutsky, BI; Gregor, RJ (2001). "Swing- and support-related muscle actions differentially trigger human walk-run and run-walk transitions". The Journal of Experimental Biology. 204 (13): 2277–87. PMID   11507111.
  12. 1 2 MacLeod, Toran D.; Hreljac, Alan; Imamura, Rodney (2006). Internal Kinetic Factors and the Preferred Transition Speed in Humans (PDF). Annual Meeting of the American Society of Biomechanics.
  13. 1 2 Hreljac, Alan (1995). "Determinants of the gait transition speed during human locomotion: Kinematic factors". Journal of Biomechanics. 28 (6): 669–77. doi:10.1016/0021-9290(94)00120-S. PMID   7601866.
  14. ↑ Getchell, N; Whitall, J (1997). "Transitions in gait as a function of physical parameters". Journal of Sport and Exercise Psychology. 19: S55.
  15. 1 2 Biewener, Andrew A. (1991). "Musculoskeletal design in relation to body size". Journal of Biomechanics. 24: 19–29. doi:10.1016/0021-9290(91)90374-V. PMID   1791177.
  16. ↑ A. A. Biewener; Taylor, CR (1986-07-01). "Bone strain: A determinant of gait and speed?". Journal of Experimental Biology. 123 (1): 383–400. PMID   3746195.
  17. ↑ Farley, Claire T.; Taylor, C. Richard (1991). "A Mechanical Trigger for the Trot-Gallop Transition in Horses". Science. 253 (5017): 306–8. Bibcode:1991Sci...253..306F. doi:10.1126/science.1857965. PMID   1857965.
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  19. ↑ Hreljac, Alan; Arata, Alan; Ferber, Reed; Mercer, John A.; Row, Brandi S. (2001). "An Electromyographical Analysis of the Role of Dorsiflexors on the Gait Transition During Human Locomotion". Journal of Applied Biomechanics. 17 (4): 287–96. doi:10.1123/jab.17.4.287.
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