Editing Long-distance running (section)

==Physiology==
Humans have been considered among the best distance runners among all running animals: game animals are faster over short distances, but they have less endurance than humans.<ref name="CarrierKapporKimurNickelsSatwantiSoTrinkaus1984">Carrier, D. R., Kapoor, A. K., Kimura, T., Nickels, M. K., Satwanti, Scott, E. C., So, J. K., & Trinkaus, E. (1984). The energetic paradox of human running and hominid evolution. ''Current Anthropology'', Vol. 25, No. 4 (August - October 1984), pp. 483-495.</ref> Unlike other primates whose bodies are suited to walk on four legs or climb trees, the human body has evolved into [[Bipedalism|upright walking]] and running around 2-3&nbsp;million years ago.<ref name="Lovejoy1988">Lovejoy, C. O. (1988). Evolution of human walking. ''Scientific American'' (0036-8733), 259 (5), p. 82.</ref>  The human body can endure long-distance running through the following attributes:
# Bone and muscle structure: unlike [[Quadrupedalism|quadruped]] mammals, which have their center of mass in front of the hind legs or limbs, in [[Bipedalism|biped]] mammals including humans the center of mass lies right above the legs. This leads to different bone and muscular demands, especially in the legs and pelvis.<ref name="Lovejoy1988" />
# Dissipation of metabolic heat: humans' ability to cool the body by [[sweating]] through the body surface provides many advantages over [[Thermoregulation|panting]] through the mouth or nose. These include a larger surface of [[evaporation]] and independence of the [[Respiratory system|respiratory cycle]].<ref name="CarrierKapporKimurNickelsSatwantiSoTrinkaus1984" />
# Increased [[tendon]] length: when compared to extant quadrupedal relatives, humans maintain longer more spring-like tendons. This allows for more efficient locomotion over flat ground using the increased energy storing capabilities of these tendon tissues.<ref>{{Cite journal |last1=Bramble |first1=Dennis M. |last2=Lieberman |first2=Daniel E. |date=November 2004 |title=Endurance running and the evolution of Homo |url=https://www.nature.com/articles/nature03052 |journal=Nature |language=en |volume=432 |issue=7015 |pages=345–352 |doi=10.1038/nature03052 |pmid=15549097 |bibcode=2004Natur.432..345B |s2cid=2470602 |issn=1476-4687}}</ref>
One distinction between upright walking and running is energy consumption during locomotion. While walking, humans use about half the energy needed to run.<ref>{{Cite journal |last1=Margaria |first1=R. |last2=Cerretelli |first2=P. |last3=Aghemo |first3=P. |last4=Sassi |first4=G. |year=1963 |title=Energy cost of running |journal=Journal of Applied Physiology |volume=18 |issue=2 |pages=367–370 |doi=10.1152/jappl.1963.18.2.367 |pmid=13932993}}</ref>

===Factors===
==== Aerobic capacity ====
One's [[aerobic capacity]] or VO<sub>2</sub>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.<ref name="Zinner2016">{{Cite book |title=Marathon Running: Physiology, Psychology, Nutrition and Training Aspects |date=2016 |publisher=Springer |isbn=9783319297286 |editor-last=Zinner |editor-first=Christoph |language=en |editor-last2=Sperlich |editor-first2=Billy}}</ref>{{rp|3}}

Aerobic capacity depends on 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.<ref name="Sarelius2010">{{Cite journal |last1=Sarelius |first1=I |last2=Pohl |first2=U |date=August 2010 |title=Control of muscle blood flow during exercise: local factors and integrative mechanisms. |journal=Acta Physiologica |volume=199 |issue=4 |pages=349–65 |doi=10.1111/j.1748-1716.2010.02129.x |pmc=3157959 |pmid=20353492}}</ref> 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.<ref name=Sarelius2010/>

Elite long-distance runners often have larger hearts and decreased resting heart rates that enable them to achieve greater aerobic capacities. Increased dimensions of 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.<ref name=Zinner2016/>{{rp|4–5}}

The amount of oxygen that blood can carry depends on [[blood volume]], which increases during a race, and the amount of hemoglobin in the blood.<ref name=Zinner2016/>{{rp|5}}<ref>{{Cite journal |last=Mairbäurl |first=Heimo |date=12 November 2013 |title=Red blood cells in sports: effects of exercise and training on oxygen supply by red blood cells |journal=Frontiers in Physiology |volume=4 |pages=332 |doi=10.3389/fphys.2013.00332 |pmc=3824146 |pmid=24273518 |doi-access=free}}</ref>

Other physiological factors affecting a marathon runner's aerobic capacity include [[Diffusing capacity|pulmonary diffusion]], mitochondria enzyme activity, and capillary density.<ref name=Zinner2016/>{{rp|4–5}}

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 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.<ref name=Zinner2016/>{{rp|7}}

==== Lactate threshold ====
A long-distance runner's velocity at the [[lactate threshold]] 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]].<ref name=Zinner2016/>{{rp|5–6}} For most runners, the aerobic zone does not begin until around 120 heartbeats per minute.<ref>{{Cite news |date=17 March 2014 |title=Lactate Threshold: What It Is And How Do You Leverage It In Training? {{!}} Competitor.com |language=en-US |work=Competitor.com |url=http://running.competitor.com/2014/03/training/lactate-threshold-leverage-training_96998 |access-date=22 May 2018}}</ref> Lactate threshold training involves tempo workouts that are meant to build strength and speed, rather than improve the cardiovascular system's efficiency in absorbing and transporting oxygen.<ref>{{Cite news |date=23 March 2015 |title=Benefits of Lactate Threshold Training for Distance Runners |language=en-US |work=Minneapolis Running |url=https://minneapolisrunning.com/anaerobic-training-for-distance-runners/ |access-date=22 May 2018}}</ref> 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.<ref>{{Cite journal |last1=Faude |first1=Oliver |last2=Kindermann |first2=Wilfried |last3=Meyer |first3=Tim |year=2009 |title=Lactate threshold concepts: how valid are they? |journal=Sports Medicine (Auckland, N.Z.) |volume=39 |issue=6 |pages=469–490 |doi=10.2165/00007256-200939060-00003 |issn=0112-1642 |pmid=19453206 |s2cid=31839157}}</ref>

==== Fuel ====
In order to sustain high-intensity running, a marathon runner must obtain sufficient [[glycogen]] stores. Glycogen can be found in 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.<ref name=Zinner2016/>{{rp|56–57}}  [[Fatty acid|Free Fatty Acids]] serve as a sparing mechanism for glycogen stores. The artificial elevation of these fatty acids along with endurance training demonstrates 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.<ref name=Zinner2016/>{{rp|51}}

Long-distance runners generally practice [[carbohydrate loading]] in their training and race preparation.<ref name=Zinner2016/>{{rp|50–55}}

==== Thermoregulation and body fluid loss ====
The [[Thermoregulation in humans|maintenance of core body temperature]] 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 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.<ref name=Zinner2016/>{{rp|69ff}}  Environmental factors can especially complicate heat regulation.<ref name=Zinner2016/>{{rp|73–74}}

====Altitude====
Since the late 1980s, Kenyans, Moroccans, and Ethiopians have dominated in major international long-distance competitions.<ref>{{Cite book |last=Roth |first=Stephen |title=Exercise Genomics |date=2011 |page=186}}</ref> 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 the [[Great Rift Valley]].<ref>{{Cite news |title=Why Are Kenya And Ethiopia So Good at Long-Distance Running? |language=en-US |work=Mpora |url=https://mpora.com/running/why-are-kenya-and-ethiopia-so-good-at-running#vzjcJtyTuOGF5k5S.97 |access-date=22 May 2018}}</ref> 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.<ref>{{Cite web |date=15 August 2018 |title=Why Ethiopia's running success is about more than poverty and altitude |url=http://www.theguardian.com/lifeandstyle/the-running-blog/2018/aug/15/why-ethiopias-running-success-is-about-more-than-poverty-and-altitude |access-date=23 December 2022 |website=The Guardian |language=en}}</ref>

=== Impact on health ===
<blockquote>"… 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 the extreme demands runners place on their bodies."<ref name="extreme">{{Cite book |last=Lieberman |first=Daniel E. |title=The Long Distance Runner's Guide to Injury Prevention and Treatment |date=2017 |publisher=Skyhorse Publishing |editor-last=Waite |editor-first=Brandee L. |pages=2–17 |chapter=History of Distance Running |editor-last2=Krabak |editor-first2=Brian J. |editor-last3=Lipman |editor-first3=Grant S. |chapter-url=https://scholar.harvard.edu/dlieberman/publications/history-distance-running}}</ref>
</blockquote>

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,<ref>{{Cite journal |last1=Hagihara |first1=Yoshinobu |last2=Nakajima |first2=Arata |last3=Fukuda |first3=Satoshi |last4=Goto |first4=Sumio |last5=Iida |first5=Haruzo |last6=Yamazaki |first6=Masashi |date=October 2009 |title=Running exercise for short duration increases bone mineral density of loaded long bones in young growing rats |journal=The Tohoku Journal of Experimental Medicine |volume=219 |issue=2 |pages=139–143 |doi=10.1620/tjem.219.139 |issn=1349-3329 |pmid=19776531 |doi-access=free}}</ref> and cholesterol is lowered.<ref>{{Cite journal |last1=Gordon |first1=Benjamin |last2=Chen |first2=Stephen |last3=Durstine |first3=J. Larry |date=July 2014 |title=The effects of exercise training on the traditional lipid profile and beyond |journal=Current Sports Medicine Reports |volume=13 |issue=4 |pages=253–259 |doi=10.1249/JSR.0000000000000073 |issn=1537-8918 |pmid=25014391 |s2cid=10408945|doi-access=free }}</ref>

However, beyond a certain point, negative consequences might occur. Older male runners (45-55) who run more than {{convert|40|mi|km|abbr=off|sp=us}} per week face reduced testosterone levels, although they are still in the normal range.<ref>{{Cite journal |last1=MacKelvie |first1=K |last2=Taunton |first2=J |last3=McKay |first3=H |last4=Khan |first4=K |date=August 2000 |title=Bone mineral density and serum testosterone in chronically trained, high mileage 40–55-year-old male runners |journal=British Journal of Sports Medicine |volume=34 |issue=4 |pages=273–278 |doi=10.1136/bjsm.34.4.273 |issn=0306-3674 |pmc=1724199 |pmid=10953900}}</ref>  Running a marathon lowers testosterone levels by 50% in men and more than doubles cortisol levels for 24 hours.<ref>{{Cite journal |last1=França |first1=Sheyla Carla A. |last2=Neto |first2=Barros |last3=Leite |first3=Turíbio |last4=Agresta |first4=Marisa Cury |last5=Lotufo |first5=Renato Fraga M. |last6=Kater |first6=Claudio E. |date=December 2006 |title=Divergent responses of serum testosterone and cortisol in athlete men after a marathon race |journal=Arquivos Brasileiros de Endocrinologia & Metabologia |volume=50 |issue=6 |pages=1082–1087 |doi=10.1590/S0004-27302006000600015 |issn=0004-2730 |pmid=17221115 |doi-access=free}}</ref>  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 the link, which may or may not be causal.<ref>{{Cite journal |last1=Wilson |first1=Mathew G. |last2=O'Hanlon |first2=Rory |last3=Prasad |first3=Sanjay |last4=Deighan |first4=Amanda |last5=MacMillan |first5=Philip |last6=Oxborough |first6=David |last7=Godfrey |first7=Richard J. |last8=Smith |first8=Gill |last9=Maceira |first9=Alicia |date=17 February 2011 |title=Diverse patterns of myocardial fibrosis in lifelong, veteran endurance athletes |journal=Journal of Applied Physiology |volume=110 |issue=6 |pages=1622–6 |doi=10.1152/japplphysiol.01280.2010 |issn=8750-7587 |pmc=3119133 |pmid=21330616}}</ref> Some studies find that running more than {{convert|20|mi|km|abbr=off|sp=us}} per week yields no lower risk for all-cause mortality than non-runners,<ref>{{Cite web |last=Design |first=ISITE |title=OASIS |url=http://www.abstractsonline.com/Plan/ViewAbstract.aspx?sKey=32617aef-b494-41b8-b2bc-3d49357a8976&cKey=984e0396-f663-4068-bbf3-1dc4023c17e1&mKey=%7BFCDB1C1C-280A-4DF1-95F8-2DAA9AB6A8BE%7D |access-date=14 June 2017 |website=abstractsonline.com}}</ref> although these studies are in conflict with large studies that show longer lifespans for any increase in exercise volume.<ref>{{Cite journal |last1=Wen |first1=Chi Pang |last2=Wai |first2=Jackson Pui Man |last3=Tsai |first3=Min Kuang |last4=Yang |first4=Yi Chen |last5=Cheng |first5=Ting Yuan David |last6=Lee |first6=Meng-Chih |last7=Chan |first7=Hui Ting |last8=Tsao |first8=Chwen Keng |last9=Tsai |first9=Shan Pou |date=1 October 2011 |title=Minimum amount of physical activity for reduced mortality and extended life expectancy: a prospective cohort study |journal=Lancet |volume=378 |issue=9798 |pages=1244–1253 |doi=10.1016/S0140-6736(11)60749-6 |issn=1474-547X |pmid=21846575 |s2cid=9538733}}</ref>

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.<ref name="driban">{{Cite journal |vauthors=Driban JB, Hootman JM, Sitler MR, Harris KP, Cattano NM |date=June 2017 |title=Is Participation in Certain Sports Associated With Knee Osteoarthritis? A Systematic Review |journal=Journal of Athletic Training |volume=52 |issue=6 |pages=497–506 |doi=10.4085/1062-6050-50.2.08 |pmc=5488840 |pmid=25574790}}</ref>

The effectiveness of [[shoe insert]]s has been contested. [[Memory foam]] and similar shoe inserts may be comfortable, but they can make foot muscles weaker in the long term.<ref>{{Cite magazine |last=Richard A. Lovett |author-link=Richard A. Lovett |date=9 June 2014 |title=A Guide to Running Shoe Inserts |url=https://www.runnersworld.com/running-gear/a-guide-to-running-shoe-inserts |magazine=[[Runner's World]] |access-date=14 April 2018}}</ref> Running shoes with special features,<ref>{{Cite news |last=Arnold |first=John |title=Expensive running shoes don't prevent injuries, but comfortable ones might |work=[[The Conversation (website)|The Conversation]] |url=http://theconversation.com/expensive-running-shoes-dont-prevent-injuries-but-comfortable-ones-might-44314 |access-date=14 April 2018}}</ref> or lack thereof in the case of minimalist designs,<ref>{{Cite journal |last=Craig Payne |date=28 January 2017 |title=RCT of traditional running shoes vs minimalist running shoes |url=https://www.runresearchjunkie.com/rct-of-traditional-running-shoes-vs-minimalist-running-shoes/ |journal=The American Journal of Sports Medicine |volume=45 |issue=5 |pages=1162–1170 |doi=10.1177/0363546516682497 |pmid=28129518 |access-date=14 April 2018 |s2cid=25996480}}</ref> do not prevent [[Running injuries|injury]]. Rather, comfortable shoes and standard running styles are safer.<ref>{{Cite web |title=The evidence-based solution for choosing running shoes |url=http://evidencebasedliving.human.cornell.edu/2015/08/11/the-evidence-on-running-shoes/ |access-date=14 April 2018 |website=evidencebasedliving.human.cornell.edu}}</ref>