Running

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Eadweard Muybridge photo sequence
People running at the 2007 Brussels 20K

Running is a means of terrestrial locomotion allowing humans and other animals to move rapidly on foot. It is simply defined in athletics terms as a gait in which at regular points during the running cycle both feet are off 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 legs in an inverted pendulum fashion.[1] A characteristic feature of a running body from the viewpoint of spring-mass mechanics, is that changes in kinetic and potential energy within a stride occur simultaneously, with energy storage accomplished by springy tendons and passive muscle elasticity.[2] The term running can refer to any of a variety of speeds ranging from jogging to sprinting.

The ancestors of mankind developed the ability to run for long distances about four and a half million years ago[citation needed], probably in order to hunt animals. Competitive running grew out of religious festivals in various areas. Records of competitive racing date back to the Tailteann Games in Ireland in 1829 BCE, while the first recorded Olympic Games took place in 776 BCE.

History

It is thought that human running evolved at least four and a half million years ago out of the ability of the ape-like Australopithecus, an early ancestor of humans, to walk upright on two legs.[3]

The theory proposed considered to be the most likely evolution of running is of early human's developing as endurance runners from the practice of persistance hunting of animals, the activity of following and chasing until a prey is too exhausted to flee, succumbing to "chase myopathy" (Sears 2001), and that human features such as the nuchal ligament, abundant sweat glands, the Achilles tendons, big knee joints and muscular glutei maximi, were changes caused by this type of activity (Bramble & Lieberman 2004, et al). [4][5][6] The theory as first proposed used comparitative physiological evidence and the natural habits of animals when running, indicating the likelihood of this activity as a successful hunting method, further evidence from observation of modern day hunting practice also indicated this likelihood (Carrier et al 1984). [7][6] According to Sears (p.12) scientific investigation (Walker & Leakey 1993) of the Nariokotome Skeleton provided further evidence for the Carrier theory. [8]

Competitive running grew out of religious festivals in various areas such as Greece, Egypt, Asia, and the Rift Valley in Africa. The Tailteann Games, an Irish sporting festival in honour of the goddess Tailtiu, dates back to 1829 BCE, and is one of the earliest records of competitive running.[9] The origins of the Olympics and Marathon running are shrouded by myth and legend, though the first recorded game took place in 776 BCE.[10]

See also : Running in Ancient Greece

Motion

Humans leap from one leg to the other while running. Each leap raises the center of gravity during take-off and lowers it on landing as the knee bends to absorb the shock. At mid arc, both feet are momentarily off the ground. This continual rise and fall of bodyweight expends energy opposing gravity and absorbing shock during take-off and landing. Running on a track requires more energy than walking to cover the same distance due to air resistance at higher speeds. As reported by Hall et al. males on a track running at a pace of 6.3 mph use 1.20 times as much energy to travel the same distance as walking at a pace of 3.15 mph, but on a treadmill running 6.3 mph uses just 1.01 times as much energy to travel the same distance as walking at 3.15 mph.[11] Therefore, running is less efficient than walking in terms of calories expended per unit distance, though it is faster.

In 2004, scientists at the University of Utah and Harvard University hypothesized that the ability of humans to sustain long-distance endurance running may have been instrumental in the evolution of the human form.[12]

File:Jeanette Kwakye cropped.jpg
Jeanette Kwakye during World Indoor Championships 2008 in Valencia

Lower body motion

Running is executed as a sequence of strides, which alternate between the two legs. Each leg's stride can be roughly divided into three phases: support, drive, and recovery. Support and drive occur when the foot is in contact with the ground. Recovery occurs when the foot is off the ground. Since only one foot is on the ground at a time in running, one leg is always in recovery, while the other goes through support and drive. Then, briefly, as the runner leaps through the air, both legs are in recovery. These phases are described in detail below.

Support

During the support phase, the foot is in contact with the ground and supports the body against gravity. The body's centre of mass is typically somewhere in the lower abdominal area between the hips. The supporting foot touches the ground slightly ahead of the point that lies directly below the body's centre of mass. The knee joint is at its greatest extension just prior to the support phase. When contact is made with the ground, the knee joint begins to flex, and the extent it flexes varies with running style. Stiff-legged running styles reduce knee flexion, and looser, or more dynamic, running styles increase it. As the supporting leg bends at the knee, the pelvis dips down on the opposite side. These motions absorb shock and are opposed by the coordinated action of several muscles. The pelvic dip is opposed by the tensor fasciae lataeilio-tibial band of the supporting leg, the hip abductor, and the abdominals and lower back muscles. The knee flexion is opposed by the Muscle contraction[clarification needed] eccentric contraction of the quadriceps muscle. The supporting hip continues to extend, and the body's centre of mass passes over the supporting leg. The knee then begins to extend, and the opposite hip rises from its brief dip. The support phase begins to transition into drive.

Drive

The support phase quickly transitions into the drive phase. The drive leg extends at the knee joint, and at the hips, such that the toe maintains contact with the ground as that leg trails behind the body. The foot pushes backward and also down, creating a diagonal force vector, which, in an efficient running style, is aimed squarely at the runner's centre of mass. Since the diagonal vector has a vertical component, the drive phase continues to provide some support against gravity and can be regarded as an extension of the support phase. During the drive, the foot may extend also, by a flexing of the soleus and gastrocnemius muscle in the calf. In some running styles, notably long-distance "shuffles" which keep the feet close to the ground, the ankle remains more or less rigid during drive. Because the knee joint straightens, though not completely, much of the power of the drive comes from the quadriceps muscle group, and in some running styles, additional power comes from the calves as they extend the foot for a longer drive. This motion is most exhibited in sprinting.

There has been much discussion about the exact nature of the drive phase, because it has now been shown scientifically that the quadriceps have no activity after the supporting phase; this has become known as the extensor paradox in running.[13] Essentially, the body automatically turns off the quadriceps after the body weight moves forward of its supporting foot. This has led to a hypothesis that there is no driving phase in running, and that the runner's own body weight is providing the propulsion during this time, essentially falling through a gravitational torque created as the general centres of mass of the runner is in a forward position from the supporting foot.

Recovery

When the driving toe loses contact with the ground, the recovery phase begins. During recovery, the hip flexes, which rapidly drives the knee forward. Much of the motion of the lower leg is driven by the forces transferred from the upper leg rather than by the action of the muscles. As the knee kicks forward, it exerts torque against the lower leg through the knee joint, causing the leg to snap upward. The degree of leg lift can be consciously adjusted by the runner, with additional muscle power. During the last stage of recovery, the hip achieves maximal flexion, and, as the lower leg rapidly unfolds, which it does in a passive way, the knee joint also reaches its greatest, though not full, extension. During this extension of the leg and flexion of the hip, the hamstring and gluteal muscles are required to stretch rapidly. Muscles which are stretched respond by contracting by a reflex action. Recovery ends when the foot comes into contact with the ground, transitioning again into the support phase.

Upper body motion

The motions of the upper body are essential to maintaining balance, and a forward motion for optimal running. They compensate for the motions of the lower body, keeping the body in rotational balance. A leg's recovery is matched by a forward drive of the opposite arm, and a leg's support and drive motions are balanced by backward movement of the opposite arm. The shoulders and torso are also involved. Because the leg drive is slower than the kick of recovery, the arm thrusting backward is slower also. The forward arm drive is more forceful and rapid.

The more force exerted by the lower body, the more exaggerated the upper body motions have to be to absorb the momentum. While it is possible to run without movements of the arms, the spine and shoulders will generally still be recruited. Using the arms to absorb the forces aids in maintaining balance at higher speed. Otherwise, optimal force would be hard to attain for fear of falling over.

Most of the energy expended in running goes to the compensating motions, and so considerable gains in running speed as well as economy can be made by eliminating wasteful or incorrect motions. For instance, if the force vector in the drive phase is aimed too far away from the centre of mass of the body, it will transfer an angular momentum to the body which has to be absorbed.

The faster the running, the more energy has to be dissipated through compensating motions throughout the entire body. This is why elite sprinters have powerful upper body physiques. As the competitive distance increases, there is a rapid drop in the upper body and overall muscle mass typically exhibited by the people who compete at a high level in each respective event. Long distance runners typically have lean muscles.

Elements of good running technique

Upright posture and a slight forward lean

Leaning forward places a runner's center of mass on the front part of the foot, which avoids landing on the heel and facilitates the use of the spring mechanism of the foot. It also makes it easier for the runner to avoid landing the foot in front of the center of mass and the resultant braking effect. While upright posture is essential, a runner should maintain a relaxed frame and use his/her core to keep posture upright and stable. This helps prevent injury as long as the body is neither rigid nor tense. The most common running mistakes are tilting the chin up and scrunching shoulders.[14]

Stride rate and types

Exercise physiologists have found that the stride rates are extremely consistent across professional runners, between 185 and 200 steps per minute. The main difference between long- and short-distance runners is the length of stride rather than the rate of stride.[15][16]

During running, the speed at which the runner moves may be calculated by multiplying the cadence (steps per second) by the stride length. Running is often measured in terms of pace[17] in minutes per mile or kilometer. Fast stride rates coincide with the rate one pumps one's arms. The faster one's arms move up and down, parallel with the body, the faster the rate of stride. Different types of stride are necessary for different types of running. When sprinting, runners stay on their toes bringing their legs up, using shorter and faster strides. Long distance runners tend to have more relaxed strides that vary.

Running injuries

Because of its high-impact nature, many injuries are associated with running. They include "runner's knee" (pain in the knee), shin splints, pulled muscles (especially the hamstring), twisted ankles, iliotibial band syndrome, plantar fasciitis, Achilles tendinitis, and stress fractures.[citation needed] Repetitive stress on the same tissues without enough time for recovery or running with improper form can lead to many of the above. Runners generally attempt to minimize these injuries by warming up before exercise,[18] focusing on proper running form, performing strength training exercises, eating a well balanced diet, allowing time for recovery, and "icing" (applying ice to sore muscles or taking an ice bath).[citation needed]

Foot blisters are also common among runners. Specialized socks greatly help to prevent blisters.

Another common, running-related injury is chafing, caused by repetitive rubbing of one piece of skin against another, or against an article of clothing. One common location for chafe to occur is the runner's upper thighs. The skin feels coarse and develops a rash-like look. A variety of deodorants and special anti-chafing creams are available to treat such problems. Chafe is also likely to occur on the nipple.

A cold bath is a popular treatment of subacute injuries or inflammation, muscular strains, and overall muscular soreness, but its efficacy is controversial.[19] Some claim that for runners in particular, ice baths offer two distinct improvements over traditional techniques.[who?] First, immersion allows controlled, even constriction around all muscles, effectively closing microscopic damage that cannot be felt and numbing the pain that can. One may step into the tub to relieve sore calves, quads, hams, and connective tissues from hips to toes will gain the same benefits, making hydrotherapy an attractive preventive regimen. Saint Andrew's cross-country coach John O'Connell, a 2:48 masters marathoner, will hit the ice baths before the ibuprofen. "Pain relievers can disguise injury", he warns. "Ice baths treat both injury and soreness." The second advantage involves a physiological reaction provoked by the large amount of muscle submerged. Assuming one has overcome the mind's initial flight response in those first torturous minutes, the body fights back by invoking a "blood rush". This rapid transmission circulation flushes the damage-inflicting waste from the system, while the cold water on the outside preserves contraction. Like an oil change or a fluid dump, the blood rush revitalizes the very areas that demand fresh nutrients.

Some runners may experience injuries when running on concrete surfaces. The problem with running on concrete is that the body adjusts to this flat surface running and some of the muscles will become weaker, along with the added impact of running on a harder surface. Therefore it is advised to change terrain occasionally – such as trail, beach, or grass running. This is more unstable ground and allows the legs to strengthen different muscles. Runners should be wary of twisting their ankles on such terrain. Running downhill also increases knee stress and should therefore be avoided. Reducing the frequency and duration can also prevent injury.

A common acronym used to help the recovery process is RICE: Rest, Ice, Compression, and Elevation.

Another injury prevention method common in the running community is stretching. Stretching is often recommended as a requirement to avoid running injuries, and it is almost uniformly performed by competitive runners of any level. Recent medical literature, however, finds mixed effects of stretching prior to running. One study found insufficient evidence to support the claim that stretching prior to running was effective in injury prevention or soreness reduction.[20] Another, however, has demonstrated that stretching prior to running increases injuries, while stretching afterwards actually decreases them.[21] The American College of Sports Medicine recommends that all stretching be done after exercise because this is when the muscles are most warmed up and capable of increasing flexibility. Recent studies have also shown that stretching will reduce the amount of strength the muscle can produce during that training session.

Proper running technique can dramatically lower the risk of running injuries.[22] Engaging the hips, driving the thigh or knee, pushing off with the ankles and not the hamstrings, pawing your legs back, and erect posture are some of the key actions in proper running technique. Running injuries can be from a lack of strength and stride length and pushing off with the hamstrings and not the ankle. The hamstrings and gluteus maximus are not involved in the push off phase of running, contrary to popular belief. [23].

Barefoot running has been promoted as a means of reducing running related injuries[24] though this position on barefoot running remains controversial and a majority of professionals advocate the wearing of appropriate shoes as the best method for avoiding injury.[25]

Recent studies have shown that runners do not have more osteoarthritis than people who do not run.[26]

Benefits of running

While there is the potential for injury in running (just as there is in any sport), there are many benefits. Some of these benefits include potential weight loss, improved cardiovascular and respiratory health (reducing the risk of cardiovascular and respiratory diseases), improved cardiovascular fitness, reduced total blood cholesterol, strengthening of bones (and potentially increased bone density), possible strengthening of the immune system and an improved self esteem and emotional state.[27] Running, like all forms of regular exercise, can effectively slow[28] or reverse[29] the effects of aging.

Running can assist people in losing weight, staying in shape and improving body composition. Running increases your metabolism. Different speeds and distances are appropriate for different individual health and fitness levels. For new runners, it takes time to get into shape. The key is consistency and a slow increase in speed and distance. While running, it is best to pay attention to how one's body feels. If a runner is gasping for breath or feels exhausted while running, it may be beneficial to slow down or try a shorter distance for a few weeks. If a runner feels that the pace or distance is no longer challenging, then the runner may want to speed up or run farther.[citation needed]

Running can also have psychological benefits, as many participants in the sport report feeling an elated, euphoric state, often referred to as a "runner's high".[30] Running is frequently recommended as therapy for people with clinical depression and people coping with addiction.[31] A possible benefit may be the enjoyment of nature and scenery, which also improves psychological well-being[32] (see Ecopsychology#Practical benefits).

In animal models, running has been shown to increase the number of newly born neurons within the brain.[33] This finding could have significant implications in aging as well as learning and memory.

Running events

Running is both a competition and a type of training for sports that have running or endurance components. As a sport, it is split into events divided by distance and sometimes includes permutations such as the obstacles in steeplechase and hurdles. Running races are contests to determine which of the competitors is able to run a certain distance in the shortest time. Today, competitive running events make up the core of the sport of athletics. Events are usually grouped into several classes, each requiring substantially different athletic strengths and involving different tactics, training methods, and types of competitors.

Running competitions have probably existed for most of humanity's history and were a key part of the ancient Olympic Games as well as the modern Olympics. The activity of running went through a period of widespread popularity in the United States during the running boom of the 1970's. Over the next two decades, as many as 25 million Americans were doing some form of running or jogging – accounting for roughly one tenth of the population.[34] Today, road racing is a popular sport among non-professional athletes, who included over 7.7 million people in America alone in 2002.[35]

Limits of speed

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.

The fastest human footspeed on record is 44.72 km/h (27.79 mph), seen during a 100-meter sprint (average speed between the 60th and the 80th meter) by Usain Bolt.[36]

Running speed over increasing distance

Distance metres Men m/sec Women m/sec
100 10.44 9.53
200 10.42 9.37
400 9.26 8.44
800 7.92 7.06
1,000 7.58 6.71
1,500 7.28 6.51
1,609 mile 7.22 6.36
2,000 7.02 6.15
3,000 6.81 6.17
5,000 6.60 5.87
10,000 track 6.34 5.64
10,000 road 6.23 5.49
15,000 road 6.02 5.38
20,000 track 5.91 5.09
20,000 road 6.02 5.30
21,097 Half marathon 6.02 5.29
21,285 One hour run 5.91 5.14
25,000 track 5.63 4.78
25,000 road 5.80 5.22
30,000 track 5.60 4.72
30,000 road 5.69 5.06
42,195 Marathon 5.67 5.19
90,000 Comrades 4.68 4.23
100,000 4.46 4.24
273,366 24-hour run 3.16 2.82

Events by type

Track running

Track running events are individual or relay events with athletes racing over specified distances on an oval running track. The events are categorised as sprints, middle and long-distance, and hurdling.

Road running

Road running takes place on a measured course over an established road (as opposed to track and cross country running). These events normally range from distances of 5 kilometers to longer distances such as half marathons and marathons, and they may involve large numbers of runners or wheelchair entrants.

Cross country running

Cross country running takes place over open or rough terrain. The courses used at these events may include grass, mud, woodlands, hills, flat ground and water. It is a popular participatory sport, and is one of the events which, along with track and field, road running, and racewalking, makes up the umbrella sport of athletics.

Events by distance

Sprints

Sprints are short running events in athletics and track and field. Races over short distances are among the oldest running competitions. The first 13 editions of the Ancient Olympic Games featured only one event – the stadion race, which was a race from one end of the stadium to the other.[37] There are three sprinting events which are currently held at the Olympics and outdoor World Championships: the 100 metres, 200 metres, and 400 metres. These events have their roots in races of imperial measurements which were later altered to metric: the 100 m evolved from the 100 yard dash,[38] the 200 m distances came from the furlong (or 1/8 of a mile),[39] and the 400 m was the successor to the 440 yard dash or quarter-mile race.[40]

At the professional level, sprinters begin the race by assuming a crouching position in the starting blocks before leaning forward and gradually moving into an upright position as the race progresses and momentum is gained.[41] Athletes remain in the same lane on the running track throughout all sprinting events,[40] with the sole exception of the 400 m indoors. Races up to 100 m are largely focused upon acceleration to an athlete's maximum speed.[41] All sprints beyond this distance increasingly incorporate an element of endurance.[42] Human physiology dictates that a runner's near-top speed cannot be maintained for more than thirty seconds or so as lactic acid builds up and leg muscles begin to be deprived of oxygen.[40]

The 60 metres is a common indoor event and it an indoor world championship event. Other less-common events include the 50 metres, 55 metres, 300 metres and 500 metres which are used in some high and collegiate competitions in the United States. The 150 metres, though rarely competed, has a star-studded history: Pietro Mennea set a world best in 1983,[43] Olympic champions Michael Johnson and Donovan Bailey went head-to-head over the distance in 1997,[44] and Usain Bolt improved Mennea's record in 2009.[43]

Middle distance

Middle distance running events are track races longer than sprints up to 3000 metres. The standard middle distances are the 800 metres, 1500 metres and mile run, although the 3000 metres may also be classified as a middle distance event.[45] The 880 yard run, or half mile, was the forebear to the 800 m distance and it has its roots in competitions in the United Kingdom in the 1830s.[46] The 1500 m came about as a result of running three laps of a 500 m track, which was commonplace in continental Europe in the 1900s.[47]

See also

References

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  21. ^ Stretching and running injuries
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  29. ^ Exercise 'can reverse ageing'
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  47. ^ 1500 m – Introduction. IAAF. Retrieved 5 April 2010.

External links