Editing Long-distance running (section)

==== 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}}