111-543: Robyn Benincasa is an American endurance racer , adventure racer , author, and motivational speaker . She was a competitor in several seasons of the Eco-Challenge: The Expedition Race reality television show. Her team won the 2000 Eco-Challenge in Borneo . She went on to found or co-found two companies focused on team-building for corporate clients. She is the founder of Project Athena ,
222-583: A cascade method, Swiss chemist and physicist Raoul Pierre Pictet evaporated liquid sulfur dioxide in order to liquefy carbon dioxide, which in turn was evaporated to cool oxygen gas enough to liquefy it. He sent a telegram on December 22, 1877, to the French Academy of Sciences in Paris announcing his discovery of liquid oxygen . Just two days later, French physicist Louis Paul Cailletet announced his own method of liquefying molecular oxygen. Only
333-522: A nonprofit organization that helps women who have experienced medical challenges to fulfill their athletic ambitions. She holds three Guinness World Records . While serving as a firefighter in San Diego, California , Benincasa became a successful endurance racer and triathlete . In 1995, she was a member of the second American team to complete the Raid Gauloises adventure race. In 1997, she
444-477: A chemical element. The name oxygen was coined in 1777 by Antoine Lavoisier , who first recognized oxygen as a chemical element and correctly characterized the role it plays in combustion. Common industrial uses of oxygen include production of steel , plastics and textiles , brazing, welding and cutting of steels and other metals , rocket propellant , oxygen therapy , and life support systems in aircraft , submarines , spaceflight and diving . One of
555-434: A few drops of the liquid were produced in each case and no meaningful analysis could be conducted. Oxygen was liquefied in a stable state for the first time on March 29, 1883, by Polish scientists from Jagiellonian University , Zygmunt Wróblewski and Karol Olszewski . In 1891 Scottish chemist James Dewar was able to produce enough liquid oxygen for study. The first commercially viable process for producing liquid oxygen
666-540: A historic method for hunting among the San of the Kalahari , American Indians , and Aboriginal Australians . In this method, the hunter would run at a slow and steady pace for between one hour and a few days, in an area where the animal has no place to hide. The animal, running in spurts, has to stop to pant to cool itself, but as the chase goes on it would not have enough time before it has to start running again, and after
777-481: A light sky-blue color caused by absorption in the red (in contrast with the blue color of the sky, which is due to Rayleigh scattering of blue light). High-purity liquid O 2 is usually obtained by the fractional distillation of liquefied air. Liquid oxygen may also be condensed from air using liquid nitrogen as a coolant. Liquid oxygen is a highly reactive substance and must be segregated from combustible materials. The spectroscopy of molecular oxygen
888-564: A major role in absorbing energy from singlet oxygen and converting it to the unexcited ground state before it can cause harm to tissues. The common allotrope of elemental oxygen on Earth is called dioxygen , O 2 , the major part of the Earth's atmospheric oxygen (see Occurrence ). O 2 has a bond length of 121 pm and a bond energy of 498 kJ/mol . O 2 is used by complex forms of life, such as animals, in cellular respiration . Other aspects of O 2 are covered in
999-410: A marathon runner's ability to sustain higher intensities for longer periods of time. The prolonged sustenance of running intensity is attributed to a high turnover rate of fatty acids that allows the runner to preserve glycogen stores later into the race. Long-distance runners generally practice carbohydrate loading in their training and race preparation. The maintenance of core body temperature
1110-734: A means to improve cardiovascular health. Endurance running is often a component of physical military training . Long-distance running as a form of tradition or ceremony is known among the Hopi and Tarahumara people , among others. In the sport of athletics , long-distance events are defined as races covering 3 km (1.9 mi) and above. The three most common types are track running , road running , and cross country running , all of which are defined by their terrain – all-weather tracks , roads, and natural terrain, respectively. Anthropological observations of modern hunter-gatherer communities have provided accounts for long-distance running as
1221-438: A part of air that he called spiritus nitroaereus . In one experiment, he found that placing either a mouse or a lit candle in a closed container over water caused the water to rise and replace one-fourteenth of the air's volume before extinguishing the subjects. From this, he surmised that nitroaereus is consumed in both respiration and combustion. Mayow observed that antimony increased in weight when heated, and inferred that
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#17328011415771332-404: A process called eutrophication and the decay of these organisms and other biomaterials may reduce the O 2 content in eutrophic water bodies. Scientists assess this aspect of water quality by measuring the water's biochemical oxygen demand , or the amount of O 2 needed to restore it to a normal concentration. Paleoclimatologists measure the ratio of oxygen-18 and oxygen-16 in
1443-425: A race, and the amount of hemoglobin in the blood. Other physiological factors affecting a marathon runner's aerobic capacity include pulmonary diffusion , mitochondria enzyme activity, and capillary density. A long-distance runner's running economy is their steady state requirement for oxygen at specific speeds and helps explain differences in performance for runners with very similar aerobic capacities. This
1554-459: A result of these factors, weather can play an integral role in racing conditions. Cross country is both an individual and team sport, as runners are judged on an individual basis and a points-scoring method is used for teams. Competitions are typically races of 4 km (2.5 mi) or more which are usually held in autumn and winter. Cross country's most successful athletes often compete in long-distance track and road events as well. The history of
1665-458: A small proportion of manganese dioxide. Oxygen levels in the atmosphere are trending slightly downward globally, possibly because of fossil-fuel burning. At standard temperature and pressure , oxygen is a colorless, odorless, and tasteless gas with the molecular formula O 2 , referred to as dioxygen. As dioxygen , two oxygen atoms are chemically bound to each other. The bond can be variously described based on level of theory, but
1776-449: A triplet electronic ground state . An electron configuration with two unpaired electrons, as is found in dioxygen orbitals (see the filled π* orbitals in the diagram) that are of equal energy—i.e., degenerate —is a configuration termed a spin triplet state. Hence, the ground state of the O 2 molecule is referred to as triplet oxygen . The highest-energy, partially filled orbitals are antibonding , and so their filling weakens
1887-566: A while would collapse from exhaustion and heat. The skeletal structure of a 12-year-old Nariokatome boy has been suggested as proof that early humans from 1.5 million years ago ate more meat and fewer plants, and hunted by running down animals. With developments in agriculture and culture, long-distance running took more and more purposes other than hunting: religious ceremonies, delivering messages for military and political purposes, and sport. Running messengers are reported from early Sumer , were named lasimu as military men as well as
1998-580: Is a corrosive byproduct of smog and thus an air pollutant . Oxygen was isolated by Michael Sendivogius before 1604, but it is commonly believed that the element was discovered independently by Carl Wilhelm Scheele , in Uppsala , in 1773 or earlier, and Joseph Priestley in Wiltshire , in 1774. Priority is often given for Priestley because his work was published first. Priestley, however, called oxygen "dephlogisticated air", and did not recognize it as
2109-457: Is a combination of cycling and distance running. Previous versions of the modern pentathlon incorporated a three or four-kilometre (1.9–2.5 mi) run, but changes to the official rules in 2008 meant the running sections are now divided into three separate legs of one kilometre each (0.6 mi). Depending on the rules and terrain, navigation sports such as foot orienteering and rogaining may contain periods of endurance running within
2220-477: Is absorbed by specialized respiratory organs called gills , through the skin or via the gut ; in terrestrial animals such as tetrapods , oxygen in air is actively taken into the body via specialized organs known as lungs , where gas exchange takes place to diffuse oxygen into the blood and carbon dioxide out, and the body's circulatory system then transports the oxygen to other tissues where cellular respiration takes place. However in insects ,
2331-601: Is aerobic respiration. This occurs when oxygen is present, and the body can utilize oxygen to help generate energy and muscle activity. On the other side, anaerobic respiration occurs when the body is deprived of oxygen, and this is common towards the final stretch of races when there is a drive to speed up to a greater intensity. Overall, both types of respiration are used by endurance runners quite often but are very different from each other. Among mammals , humans are well adapted for running significant distances, particularly so among primates . The capacity for endurance running
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#17328011415772442-403: Is also found in migratory ungulates and a limited number of terrestrial carnivores, such as bears, dogs, wolves , and hyenas . In modern human society, long-distance running has multiple purposes: people may engage in it for physical exercise , for recreation , as a means of travel, as a competitive sport, for economic reasons, or cultural reasons. Long-distance running can also be used as
2553-513: Is associated with the atmospheric processes of aurora and airglow . The absorption in the Herzberg continuum and Schumann–Runge bands in the ultraviolet produces atomic oxygen that is important in the chemistry of the middle atmosphere. Excited-state singlet molecular oxygen is responsible for red chemiluminescence in solution. Table of thermal and physical properties of oxygen (O 2 ) at atmospheric pressure: Naturally occurring oxygen
2664-472: Is composed of three stable isotopes , O , O , and O , with O being the most abundant (99.762% natural abundance ). Most O is synthesized at the end of the helium fusion process in massive stars but some is made in the neon burning process . O is primarily made by the burning of hydrogen into helium during the CNO cycle , making it a common isotope in the hydrogen burning zones of stars. Most O
2775-412: Is crucial to a marathon runner's performance and health. An inability to reduce rising core body temperature can lead to hyperthermia . In order to reduce body heat, the metabolically produced heat needs to be removed from the body via sweating, which in turn requires rehydration to compensate for. Replacement of fluid is limited but can help keep the body's internal temperatures cooler. Fluid replacement
2886-407: Is energy consumption during locomotion. While walking, humans use about half the energy needed to run. One's aerobic capacity or VO 2 Max is the ability to maximally take up and consume oxygen during exhaustive exercise. Long-distance runners typically perform at around 75–85% of peak aerobic capacity, while short-distance runners perform at closer to 100% of peak. Aerobic capacity depends on
2997-554: Is exclusively found in racing sports . Most of these are individual sports , although team and relay forms also exist. The most prominent long-distance running sports are grouped within the sport of athletics , where running competitions are held on strictly defined courses, and the fastest runner to complete the distance wins. The foremost types are long-distance track running , road running and cross-country running . Other less popular variants such as fell running , trail running , mountain running , and tower running combine
3108-407: Is often measured by the volume of oxygen consumed, either in liters or milliliters, per kilogram of body weight per minute (L/kg/min or mL/kg/min). As of 2016 the physiological basis for this was uncertain, but it seemed to depend on the cumulative years of running and reaches a cap that longer individual training sessions cannot overcome. A long-distance runner's velocity at the lactate threshold
3219-447: Is oxygen as a component of water, the major constituent of lifeforms. Oxygen in Earth's atmosphere is produced by biotic photosynthesis , in which photon energy in sunlight is captured by chlorophyll to split water molecules and then react with carbon dioxide to produce carbohydrates and oxygen is released as a byproduct . Oxygen is too chemically reactive to remain a free element in air without being continuously replenished by
3330-811: Is physiologically challenging during the exercise of this intensity due to the inefficient emptying of the stomach. Partial fluid replacement can serve to avoid a marathon runner's body overheating but not enough to keep pace with the loss of fluid via sweat evaporation. Environmental factors can especially complicate heat regulation. Since the late 1980s, Kenyans, Moroccans, and Ethiopians have dominated in major international long-distance competitions. The high altitude of these countries has been proven to help these runners achieve more success. High altitude, combined with endurance training, can lead to an increase in red blood cells, allowing increased oxygen delivery via arteries. The majority of these East African successful runners come from three mountain districts that run along
3441-441: Is produced when N (made abundant from CNO burning) captures a He nucleus, making O common in the helium-rich zones of evolved, massive stars . Fifteen radioisotopes have been characterized, ranging from O to O. The most stable are O with a half-life of 122.24 seconds and O with a half-life of 70.606 seconds. All of the remaining radioactive isotopes have half-lives that are less than 27 seconds and
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3552-408: Is reasonably and simply described as a covalent double bond that results from the filling of molecular orbitals formed from the atomic orbitals of the individual oxygen atoms, the filling of which results in a bond order of two. More specifically, the double bond is the result of sequential, low-to-high energy, or Aufbau , filling of orbitals, and the resulting cancellation of contributions from
3663-503: Is strongly correlated to their performance. The lactate threshold is the cross-over point between predominantly aerobic energy usage and anaerobic energy usage and is considered a good indicator of the body's ability to efficiently process and transfer chemical energy into mechanical energy . For most runners, the aerobic zone does not begin until around 120 heartbeats per minute. Lactate threshold training involves tempo workouts that are meant to build strength and speed, rather than improve
3774-712: Is temperature-dependent, and about twice as much ( 14.6 mg/L ) dissolves at 0 °C than at 20 °C ( 7.6 mg/L ). At 25 °C and 1 standard atmosphere (101.3 kPa ) of air, freshwater can dissolve about 6.04 milliliters (mL) of oxygen per liter , and seawater contains about 4.95 mL per liter. At 5 °C the solubility increases to 9.0 mL (50% more than at 25 °C) per liter for freshwater and 7.2 mL (45% more) per liter for sea water. Oxygen condenses at 90.20 K (−182.95 °C, −297.31 °F) and freezes at 54.36 K (−218.79 °C, −361.82 °F). Both liquid and solid O 2 are clear substances with
3885-435: Is the result of the oxygen cycle . This biogeochemical cycle describes the movement of oxygen within and between its three main reservoirs on Earth: the atmosphere, the biosphere, and the lithosphere . The main driving factor of the oxygen cycle is photosynthesis , which is responsible for modern Earth's atmosphere. Photosynthesis releases oxygen into the atmosphere, while respiration , decay , and combustion remove it from
3996-463: Is unusual among the planets of the Solar System in having such a high concentration of oxygen gas in its atmosphere: Mars (with 0.1% O 2 by volume) and Venus have much less. The O 2 surrounding those planets is produced solely by the action of ultraviolet radiation on oxygen-containing molecules such as carbon dioxide. The unusually high concentration of oxygen gas on Earth
4107-522: Is usually given priority in the discovery. The French chemist Antoine Laurent Lavoisier later claimed to have discovered the new substance independently. Priestley visited Lavoisier in October 1774 and told him about his experiment and how he liberated the new gas. Scheele had also dispatched a letter to Lavoisier on September 30, 1774, which described his discovery of the previously unknown substance, but Lavoisier never acknowledged receiving it (a copy of
4218-401: The 1912 Summer Olympics . Fell running , trail running , and mountain running can all be considered variations on the traditional cross country which incorporate significant uphill and/or downhill sections as an additional challenge to the course. The term adventure running is loosely defined and can be used to describe any form of long-distance running in a natural setting, regardless of
4329-669: The Earth , the Moon , Mars , and meteorites , but were long unable to obtain reference values for the isotope ratios in the Sun , believed to be the same as those of the primordial solar nebula . Analysis of a silicon wafer exposed to the solar wind in space and returned by the crashed Genesis spacecraft has shown that the Sun has a higher proportion of oxygen-16 than does the Earth. The measurement implies that an unknown process depleted oxygen-16 from
4440-463: The Earth's crust in the form of various oxides such as water , carbon dioxide , iron oxides and silicates . All eukaryotic organisms , including plants , animals , fungi , algae and most protists , need oxygen for cellular respiration , which extracts chemical energy by the reaction of oxygen with organic molecules derived from food and releases carbon dioxide as a waste product. In aquatic animals , dissolved oxygen in water
4551-467: The Great Rift Valley . While altitude may be a contributing factor, a culture of hard work, teamwork, as well as an advanced institutional structure also contributes to their success. "… an evolutionary perspective indicates that we did not evolve to run long distances at fast speeds on a regular basis. As a result, it is unlikely there was a selection for the human body to cope with some of
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4662-565: The Greek roots ὀξύς (oxys) ( acid , literally 'sharp', from the taste of acids) and -γενής (-genēs) (producer, literally begetter), because he mistakenly believed that oxygen was a constituent of all acids. Chemists (such as Sir Humphry Davy in 1812) eventually determined that Lavoisier was wrong in this regard, but by then the name was too well established. Oxygen entered the English language despite opposition by English scientists and
4773-653: The Summer Paralympics . The World Marathon Majors series includes the six most prestigious marathon competitions at the elite level – the Berlin , Boston , Chicago , London , Tokyo , and New York City marathons. The Tokyo Marathon was most recently added to the World Marathon Majors in 2012. Ekiden contests – which originated in Japan and remain common there – are a relay race variation on
4884-979: The Yukon River in Canada. She secured her third Guinness Record in 2014, for the greatest distance travelled by a woman on a stand-up paddleboard in still water in 24 hours, covering a total of 146 kilometres (91 mi). She accomplished this by paddling laps around an island in Huntington Harbor in Huntington Beach, California . In 1998, Benincasa, fellow-firefighter and Eco-Internet teammate Ian Adamson , and ultra-marathoner Liz Hafer founded Colorado Adventure Training. The three co-founders brought their experience as teammates in endurance races to build team-building experiences that encourage participants to learn to ask each other for support and to provide it. Following Adamson's dropping Benincasa from
4995-470: The shells and skeletons of marine organisms to determine the climate millions of years ago (see oxygen isotope ratio cycle ). Seawater molecules that contain the lighter isotope , oxygen-16, evaporate at a slightly faster rate than water molecules containing the 12% heavier oxygen-18, and this disparity increases at lower temperatures. During periods of lower global temperatures, snow and rain from that evaporated water tends to be higher in oxygen-16, and
5106-430: The thermal decomposition of potassium nitrate . In Bugaj's view, the isolation of oxygen and the proper association of the substance to that part of air which is required for life, provides sufficient evidence for the discovery of oxygen by Sendivogius. This discovery of Sendivogius was however frequently denied by the generations of scientists and chemists which succeeded him. It is also commonly claimed that oxygen
5217-557: The 17th and the 18th century but none of them recognized it as a chemical element . This may have been in part due to the prevalence of the philosophy of combustion and corrosion called the phlogiston theory , which was then the favored explanation of those processes. Established in 1667 by the German alchemist J. J. Becher , and modified by the chemist Georg Ernst Stahl by 1731, phlogiston theory stated that all combustible materials were made of two parts. One part, called phlogiston,
5328-500: The 2001 Eco-Challenge in New Zealand. Benincasa and Team Earthlink finished in fourth place. Benincasa has earned three Guinness World Records. Her first was in 2010, for the farthest distance travelled by a woman by canoe or kayak on flat water. In 2011, Benincasa set a Guinness World Record for the farthest distance travelled by a woman by canoe or kayak in 24 hours on moving water. She kayaked 371.92 kilometres (231.10 mi) on
5439-503: The 20th century: the oval running tracks were standardised to 400 metres in distance and cinder tracks were replaced by synthetic all-weather running track of asphalt and rubber from the mid-1960s onwards. It was not until the 1912 Stockholm Olympics that the standard long-distance track events of 5000 metres and 10,000 metres were introduced. Long-distance road running competitions are mainly conducted on courses of paved or tarmac roads, although major events often finish on
5550-531: The 2s electrons, after sequential filling of the low σ and σ orbitals; σ overlap of the two atomic 2p orbitals that lie along the O–O molecular axis and π overlap of two pairs of atomic 2p orbitals perpendicular to the O–O molecular axis, and then cancellation of contributions from the remaining two 2p electrons after their partial filling of the π orbitals. This combination of cancellations and σ and π overlaps results in dioxygen's double-bond character and reactivity, and
5661-536: The American scientist Robert H. Goddard became the first person to develop a rocket engine that burned liquid fuel; the engine used gasoline for fuel and liquid oxygen as the oxidizer . Goddard successfully flew a small liquid-fueled rocket 56 m at 97 km/h on March 16, 1926, in Auburn, Massachusetts , US. In academic laboratories, oxygen can be prepared by heating together potassium chlorate mixed with
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#17328011415775772-473: The Eco-Internet team in 2001, Benincasa ended her relationship with the company. She later founded Human Synergy, Inc., also focusing on corporate team-building, using a framework of "Eight Essential Elements of Human Synergy." In 2012, she published the book How Winning Works : 8 Essential Leadership Lessons From The Toughest Teams On Earth . Benincasa was diagnosed with osteoarthritis in 2007 and
5883-484: The Philosopher's Stone drawn from the source of nature and manual experience"] (1604) described a substance contained in air, referring to it as 'cibus vitae' (food of life, ) and according to Polish historian Roman Bugaj, this substance is identical with oxygen. Sendivogius, during his experiments performed between 1598 and 1604, properly recognized that the substance is equivalent to the gaseous byproduct released by
5994-438: The Sun's disk of protoplanetary material prior to the coalescence of dust grains that formed the Earth. Oxygen presents two spectrophotometric absorption bands peaking at the wavelengths 687 and 760 nm . Some remote sensing scientists have proposed using the measurement of the radiance coming from vegetation canopies in those bands to characterize plant health status from a satellite platform. This approach exploits
6105-833: The United States made road running a common pastime and also increased its popularity at the elite level. The marathon is the only road running event featured at the World Athletics Championships and the Summer Olympics , although there is also the World Athletics Half Marathon Championships held every two years. The marathon is also the only road running event featured at the World Para Athletics Championships and
6216-400: The United States, men race 8,000 or 10,000 meters, depending on their division, whereas women race 6,000 meters. The Summer Olympics features four long-distance running events: the 3000 metres steeplechase (which also involves jumping over barriers and water), the 5000 metres , 10,000 metres and marathon (42.195 kilometres, or 26 miles and 385 yards). Humans have been considered among
6327-493: The atmosphere. In the present equilibrium, production and consumption occur at the same rate. Free oxygen also occurs in solution in the world's water bodies. The increased solubility of O 2 at lower temperatures (see Physical properties ) has important implications for ocean life, as polar oceans support a much higher density of life due to their higher oxygen content. Water polluted with plant nutrients such as nitrates or phosphates may stimulate growth of algae by
6438-459: The best distance runners among all running animals: game animals are faster over short distances, but they have less endurance than humans. Unlike other primates whose bodies are suited to walk on four legs or climb trees, the human body has evolved into upright walking and running around 2-3 million years ago. The human body can endure long-distance running through the following attributes: One distinction between upright walking and running
6549-412: The bond order from three to two. Because of its unpaired electrons, triplet oxygen reacts only slowly with most organic molecules, which have paired electron spins; this prevents spontaneous combustion. In the triplet form, O 2 molecules are paramagnetic . That is, they impart magnetic character to oxygen when it is in the presence of a magnetic field, because of the spin magnetic moments of
6660-426: The cardiovascular system's efficiency in absorbing and transporting oxygen. By running at your lactate threshold, your body will become more efficient at clearing lactate and reusing it to fuel your muscles. Uncertainty exists in regard to how lactate threshold affects endurance performance. In order to sustain high-intensity running, a marathon runner must obtain sufficient glycogen stores. Glycogen can be found in
6771-469: The carriages of aristocrats around the 18th century, and who also ran errands over distances for their masters. Foot racing competitions evolved from wagers between aristocrats, who pitted their footman against that of another aristocrat in order to determine a winner. The sport became professionalised as footmen were hired specifically on their athletic ability and began to devote their lives to training for gambling events. The amateur sports movement in
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#17328011415776882-511: The challenge of distance with a significant incline or change of elevation as part of the course. Multisport races frequently include endurance running. Triathlon , as defined by the International Triathlon Union , may feature running sections ranging from five kilometres (3.1 miles) to the marathon distance (42.195 kilometres, or 26 miles and 385 yards), depending on the race type . The related sport of duathlon
6993-443: The competition. Variants of adventure racing may also combine navigational skills and endurance running in this manner. The history of long-distance track running events are tied to the track and field stadia where they are held. Oval circuits allow athletes to cover long distances in a confined area. Early tracks were usually on flattened earth or were simply marked areas of grass. The style of running tracks became refined during
7104-460: The context of track and field sports events. These include multiday races , ultramarathons , and long-distance races in extreme conditions or measuring hundreds or thousands of miles . Beyond these, records and stand-alone achievements, rather than regular events, exist for individuals who have achieved running goals of a unique nature, such as running across or around continents (see lists of runners: America , Australia ) or running around
7215-444: The diatomic elemental molecules in those gases. The first commercial method of producing oxygen was chemical, the so-called Brin process involving a reversible reaction of barium oxide . It was invented in 1852 and commercialized in 1884, but was displaced by newer methods in early 20th century. By the late 19th century scientists realized that air could be liquefied and its components isolated by compressing and cooling it. Using
7326-466: The electron spins are paired. It is much more reactive with common organic molecules than is normal (triplet) molecular oxygen. In nature, singlet oxygen is commonly formed from water during photosynthesis, using the energy of sunlight. It is also produced in the troposphere by the photolysis of ozone by light of short wavelength and by the immune system as a source of active oxygen. Carotenoids in photosynthetic organisms (and possibly animals) play
7437-463: The extreme demands runners place on their bodies." The impact of long-distance running on human health is generally positive. Various organs and systems in the human body are improved: bone mineral density is increased, and cholesterol is lowered. However, beyond a certain point, negative consequences might occur. Older male runners (45-55) who run more than 40 miles (64 kilometers) per week face reduced testosterone levels, although they are still in
7548-572: The fact that the Englishman Priestley had first isolated the gas and written about it. This is partly due to a poem praising the gas titled "Oxygen" in the popular book The Botanic Garden (1791) by Erasmus Darwin , grandfather of Charles Darwin . John Dalton 's original atomic hypothesis presumed that all elements were monatomic and that the atoms in compounds would normally have the simplest atomic ratios with respect to one another. For example, Dalton assumed that water's formula
7659-470: The first International Cross Country Championships in 1903. The annual World Athletics Cross Country Championships was inaugurated in 1973 and this remains the highest level of competition for the sport. A number of continental cross country competitions are held, with championships taking place in Africa , Asia , Europe , Oceania , North America and South America . The sport has retained its status at
7770-399: The first known experiments on the relationship between combustion and air was conducted by the 2nd century BCE Greek writer on mechanics, Philo of Byzantium . In his work Pneumatica , Philo observed that inverting a vessel over a burning candle and surrounding the vessel's neck with water resulted in some water rising into the neck. Philo incorrectly surmised that parts of the air in
7881-411: The heart enable an individual to achieve a greater stroke volume . A concomitant decrease in stroke volume occurs with the initial increase in heart rate at the onset of exercise. Despite an increase in cardiac dimensions, a marathoner's aerobic capacity is confined to this capped and ever-decreasing heart rate. The amount of oxygen that blood can carry depends on blood volume , which increases during
7992-399: The idea; instead, it was based on observations of what happens when something burns, that most common objects appear to become lighter and seem to lose something in the process. Polish alchemist , philosopher , and physician Michael Sendivogius (Michał Sędziwój) in his work De Lapide Philosophorum Tractatus duodecim e naturae fonte et manuali experientia depromti ["Twelve Treatises on
8103-560: The king's officials who disseminated documents throughout the kingdom by running. Ancient Greece was famous for its running messengers, who were named hemerodromoi , meaning "day runners". One of the most famous running messengers is Pheidippides , who according to the legend ran from Marathon to Athens to announce the victory of the Greek over the Persians in the Battle of Marathon in 490 B.C. He collapsed and died as he delivered
8214-545: The late 19th century marginalised competitions based on the professional, gambling model. The 1896 Summer Olympics saw the birth of the modern marathon and the event led to the growth of road running competitions through annual public events such as the Boston Marathon (first held in 1897) and the Lake Biwa Marathon and Fukuoka Marathons , which were established in the 1940s. The 1970s running boom in
8325-504: The letter was found in Scheele's belongings after his death). Lavoisier conducted the first adequate quantitative experiments on oxidation and gave the first correct explanation of how combustion works. He used these and similar experiments, all started in 1774, to discredit the phlogiston theory and to prove that the substance discovered by Priestley and Scheele was a chemical element . In one experiment, Lavoisier observed that there
8436-621: The link, which may or may not be causal. Some studies find that running more than 20 miles (32 kilometers) per week yields no lower risk for all-cause mortality than non-runners, although these studies are in conflict with large studies that show longer lifespans for any increase in exercise volume. Elite-level long-distance running is associated with a three to seven times higher risk of the knee osteoarthritis later in life compared to non-runners. The effectiveness of shoe inserts has been contested. Memory foam and similar shoe inserts may be comfortable, but they can make foot muscles weaker in
8547-412: The long term. Running shoes with special features, or lack thereof in the case of minimalist designs, do not prevent injury . Rather, comfortable shoes and standard running styles are safer. Many sporting activities feature significant levels of running under prolonged periods of play, especially during ball sports like association football and rugby league . However, continuous endurance running
8658-428: The majority of these have half-lives that are less than 83 milliseconds. The most common decay mode of the isotopes lighter than O is β decay to yield nitrogen, and the most common mode for the isotopes heavier than O is beta decay to yield fluorine . Oxygen is the most abundant chemical element by mass in the Earth's biosphere , air, sea and land. Oxygen is the third most abundant chemical element in
8769-453: The marathon, in contrast to the typically individual sport of road running. Cross-country running is the most naturalistic form of long-distance running in athletics as competitions take place on open-air courses over surfaces such as grass, woodland trails, earth , or mountains. In contrast to the relatively flat courses in track and road races, cross country usually incorporates obstacles such as muddy sections, logs, and mounds of earth. As
8880-643: The message "we won". While there are debates around the accuracy of this historical legend, whether Pheidippides ran from Marathon to Athens or between other cities, how far this was, and if he was the one to deliver the victory message, the marathon running event of 26.2 miles / 42.195 km is based on this legend. Typical long-distance track races range from 3000 metres (1.87 miles) to 10,000 metres (6.2 miles), cross country races usually cover 5 to 12 km (3 to 7 1 ⁄ 2 miles), while road races can be significantly longer, reaching 100 km (62 mi) and beyond. In collegiate cross-country races in
8991-418: The most successful and biodiverse terrestrial clade , oxygen is directly conducted to the internal tissues via a deep network of airways . Many major classes of organic molecules in living organisms contain oxygen atoms, such as proteins , nucleic acids , carbohydrates and fats , as do the major constituent inorganic compounds of animal shells, teeth, and bone. Most of the mass of living organisms
9102-494: The nitroaereus must have combined with it. He also thought that the lungs separate nitroaereus from air and pass it into the blood and that animal heat and muscle movement result from the reaction of nitroaereus with certain substances in the body. Accounts of these and other experiments and ideas were published in 1668 in his work Tractatus duo in the tract "De respiratione". Robert Hooke , Ole Borch , Mikhail Lomonosov , and Pierre Bayen all produced oxygen in experiments in
9213-486: The normal range. Running a marathon lowers testosterone levels by 50% in men and more than doubles cortisol levels for 24 hours. Low testosterone is thought to be a physiological adaptation to the sport, as excess muscle caused may be shed through lower testosterone, yielding a more efficient runner. Veteran, lifelong endurance athletes have been found to have more heart scarring than control groups, but replication studies and larger studies should be done to firmly establish
9324-454: The photosynthetic activities of autotrophs such as cyanobacteria , chloroplast -bearing algae and plants. A much rarer triatomic allotrope of oxygen , ozone ( O 3 ), strongly absorbs the UVB and UVC wavelengths and forms a protective ozone layer at the lower stratosphere , which shields the biosphere from ionizing ultraviolet radiation . However, ozone present at the surface
9435-458: The remainder of this article. Trioxygen ( O 3 ) is usually known as ozone and is a very reactive allotrope of oxygen that is damaging to lung tissue. Ozone is produced in the upper atmosphere when O 2 combines with atomic oxygen made by the splitting of O 2 by ultraviolet (UV) radiation. Since ozone absorbs strongly in the UV region of the spectrum , the ozone layer of
9546-530: The running surface. It may include river crossing, scrambling , snow, extremely high or low temperatures, and high altitudes. It has both competitive and non-competitive forms, the latter being for individual recreation or social experience. As a result, courses are often set in scenic locations and feature obstacles designed to give participants a sense of achievement. It bears similarities to running sections of adventure racing . A number of events, records, and achievements exist for long-distance running, outside
9657-634: The scholastic level, particularly in the United Kingdom and the United States. At the professional level, the foremost competitions come under the banner of the World Athletics Cross Country Tour . While cross country competitions are no longer held at the Olympics, having featured in the athletics programme from 1912 to 1924, it has been present as one of the events within the modern pentathlon competition since
9768-414: The seawater left behind tends to be higher in oxygen-18. Marine organisms then incorporate more oxygen-18 into their skeletons and shells than they would in a warmer climate. Paleoclimatologists also directly measure this ratio in the water molecules of ice core samples as old as hundreds of thousands of years. Planetary geologists have measured the relative quantities of oxygen isotopes in samples from
9879-442: The skeletal muscles and liver. With low levels of glycogen stores at the onset of the marathon, premature depletion of these stores can reduce performance or even prevent the completion of the race. ATP production via aerobic pathways can further be limited by glycogen depletion. Free Fatty Acids serve as a sparing mechanism for glycogen stores. The artificial elevation of these fatty acids along with endurance training demonstrates
9990-523: The sport is linked with the game of paper chase , or hare and hounds, where a group of runners would cover long distances to chase a leading runner, who left a trail of paper to follow. The Crick Run in England in 1838 was the first recorded instance of an organised cross-country competition. The sport gained popularity in British, then American schools in the 19th century and culminated in the creation of
10101-439: The track of a main stadium. In addition to being a common recreational sport , the elite level of the sport – particularly marathon races – is one of the most popular aspects of athletics. Road racing events can be of virtually any distance, but the most common and well-known is the marathon, half marathon , and 10 km run . The sport of road running finds its roots in the activities of footmen : male servants who ran alongside
10212-647: The transportation of large amounts of blood to and from the lungs to reach all tissues. This in turn is dependent on having a high cardiac output , sufficient levels of hemoglobin in blood and an optimal vascular system to distribute blood. A 20-fold increase of local blood flow within the skeletal muscle is necessary for endurance athletes, like marathon runners, to meet their muscles' oxygen demands at maximal exercise that are up to 50 times greater than at rest. Elite long-distance runners often have larger hearts and decreased resting heart rates that enable them to achieve greater aerobic capacities. Increased dimensions of
10323-440: The universe after hydrogen and helium . At standard temperature and pressure , two oxygen atoms will bind covalently to form dioxygen , a colorless and odorless diatomic gas with the chemical formula O 2 . Dioxygen gas currently constitutes 20.95% molar fraction of the Earth's atmosphere , though this has changed considerably over long periods of time in Earth's history . Oxygen makes up almost half of
10434-486: The universe, after hydrogen and helium. About 0.9% of the Sun 's mass is oxygen. Oxygen constitutes 49.2% of the Earth's crust by mass as part of oxide compounds such as silicon dioxide and is the most abundant element by mass in the Earth's crust . It is also the major component of the world's oceans (88.8% by mass). Oxygen gas is the second most common component of the Earth's atmosphere , taking up 20.8% of its volume and 23.1% of its mass (some 10 tonnes). Earth
10545-401: The unpaired electrons in the molecule, and the negative exchange energy between neighboring O 2 molecules. Liquid oxygen is so magnetic that, in laboratory demonstrations, a bridge of liquid oxygen may be supported against its own weight between the poles of a powerful magnet. Singlet oxygen is a name given to several higher-energy species of molecular O 2 in which all
10656-435: The upper atmosphere functions as a protective radiation shield for the planet. Near the Earth's surface, it is a pollutant formed as a by-product of automobile exhaust . At low earth orbit altitudes, sufficient atomic oxygen is present to cause corrosion of spacecraft . The metastable molecule tetraoxygen ( O 4 ) was discovered in 2001, and was assumed to exist in one of the six phases of solid oxygen . It
10767-451: The vessel were converted into the classical element fire and thus were able to escape through pores in the glass. Many centuries later Leonardo da Vinci built on Philo's work by observing that a portion of air is consumed during combustion and respiration . In the late 17th century, Robert Boyle proved that air is necessary for combustion. English chemist John Mayow (1641–1679) refined this work by showing that fire requires only
10878-486: The work of Project Athena and the 140 women the project had supported at the time. Long-distance running Long-distance running , or endurance running , is a form of continuous running over distances of at least 3 km (1.9 mi). Physiologically, it is largely aerobic in nature and requires stamina as well as mental strength. Within endurance running comes two different types of respiration . The more prominent side that runners experience more frequently
10989-420: The world . Oxygen Oxygen is a chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table , a highly reactive nonmetal , and a potent oxidizing agent that readily forms oxides with most elements as well as with other compounds . Oxygen is the most abundant element in Earth's crust , and the third-most abundant element in
11100-428: Was HO, leading to the conclusion that the atomic mass of oxygen was 8 times that of hydrogen, instead of the modern value of about 16. In 1805, Joseph Louis Gay-Lussac and Alexander von Humboldt showed that water is formed of two volumes of hydrogen and one volume of oxygen; and by 1811 Amedeo Avogadro had arrived at the correct interpretation of water's composition, based on what is now called Avogadro's law and
11211-408: Was first discovered by Swedish pharmacist Carl Wilhelm Scheele . He had produced oxygen gas by heating mercuric oxide (HgO) and various nitrates in 1771–72. Scheele called the gas "fire air" because it was then the only known agent to support combustion. He wrote an account of this discovery in a manuscript titled Treatise on Air and Fire , which he sent to his publisher in 1775. That document
11322-451: Was given off when the substance containing it was burned, while the dephlogisticated part was thought to be its true form, or calx . Highly combustible materials that leave little residue , such as wood or coal, were thought to be made mostly of phlogiston; non-combustible substances that corrode, such as iron, contained very little. Air did not play a role in phlogiston theory, nor were any initial quantitative experiments conducted to test
11433-491: Was independently developed in 1895 by German engineer Carl von Linde and British engineer William Hampson . Both men lowered the temperature of air until it liquefied and then distilled the component gases by boiling them off one at a time and capturing them separately. Later, in 1901, oxyacetylene welding was demonstrated for the first time by burning a mixture of acetylene and compressed O 2 . This method of welding and cutting metal later became common. In 1923,
11544-445: Was no overall increase in weight when tin and air were heated in a closed container. He noted that air rushed in when he opened the container, which indicated that part of the trapped air had been consumed. He also noted that the tin had increased in weight and that increase was the same as the weight of the air that rushed back in. This and other experiments on combustion were documented in his book Sur la combustion en général , which
11655-465: Was not sensibly different from that of common air , but I fancied that my breast felt peculiarly light and easy for some time afterwards." Priestley published his findings in 1775 in a paper titled "An Account of Further Discoveries in Air", which was included in the second volume of his book titled Experiments and Observations on Different Kinds of Air . Because he published his findings first, Priestley
11766-797: Was on the Mountain Dew -sponsored team in the Discovery Channel Eco-Challenge in Queensland, Australia . She was on the Eco-Internet team in 1999 and 2000, and contributed to that team's first-place victory in 2000. She was dropped from the team in 2001 due to a struggle with asthma brought on by exercise and altitude during a race in Switzerland . She was treated for the ailment, and stepped in to join Team Earthlink, which had lost one of its members for
11877-408: Was proven in 2006 that this phase, created by pressurizing O 2 to 20 GPa , is in fact a rhombohedral O 8 cluster . This cluster has the potential to be a much more powerful oxidizer than either O 2 or O 3 and may therefore be used in rocket fuel . A metallic phase was discovered in 1990 when solid oxygen is subjected to a pressure of above 96 GPa and it
11988-449: Was published in 1777. In the meantime, on August 1, 1774, an experiment conducted by the British clergyman Joseph Priestley focused sunlight on mercuric oxide contained in a glass tube, which liberated a gas he named "dephlogisticated air". He noted that candles burned brighter in the gas and that a mouse was more active and lived longer while breathing it. After breathing the gas himself, Priestley wrote: "The feeling of it to my lungs
12099-462: Was published in 1777. In that work, he proved that air is a mixture of two gases; 'vital air', which is essential to combustion and respiration, and azote (Gk. ἄζωτον "lifeless"), which did not support either. Azote later became nitrogen in English, although it has kept the earlier name in French and several other European languages. Lavoisier renamed 'vital air' to oxygène in 1777 from
12210-420: Was shown in 1998 that at very low temperatures, this phase becomes superconducting . Oxygen dissolves more readily in water than nitrogen, and in freshwater more readily than in seawater. Water in equilibrium with air contains approximately 1 molecule of dissolved O 2 for every 2 molecules of N 2 (1:2), compared with an atmospheric ratio of approximately 1:4. The solubility of oxygen in water
12321-466: Was told that she might not be able to run again. Determined to continue her athletic endeavors, she underwent hip resurfacing surgery and ran the Sedona Marathon four months later. Following her recovery, she founded Project Athena, a nonprofit organization dedicated to supporting women pursue their athletic dreams after suffering medical setbacks. In 2014, CNN named Benincasa a CNN Hero, citing
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