Editing Long-distance running (section)

===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>