Footspeed#Limits of speed

The key determinant of footspeed in sprinting is the predominance of one distinct type of muscle fibre over another, specifically the ratio of fast-twitch muscles to slow-twitch muscles in a sprinter's physical makeup. Though fast-twitch muscles produce no more energy than slow-twitch muscles when they contract, they do so more rapidly through a process of anaerobic metabolism, though at the cost of inferior efficiency over longer periods of firing.Quinn, Elizabeth. [http://sportsmedicine.about.com/od/anatomyandphysiology/a/MuscleFiberType.htm "Fast and Slow Twitch Muscle Fibers"] {{Webarchive|url=https://web.archive.org/web/20071121100903/http://sportsmedicine.about.com/od/anatomyandphysiology/a/MuscleFiberType.htm |date=2007-11-21 }}, About.com, retrieved November 26, 2007. The average human has an almost-equal ratio of fast-twitch to slow-twitch fibers, but top sprinters may have as much as 80% fast-twitch fibers, while top long-distance runners may have only 20%. This ratio is believed to have genetic origins, though some assert that it can be adjusted by muscle training.{{cite news|last=Ziegler|first=Mark|title=The NFL treats 40-yard dash times as sacred. But if those numbers are true, many players are faster than Olympic gold medalists and their clockings should be eyed with a dash of doubt|url=http://www.utsandiego.com/uniontrib/20050418/news_1s18forty.html|access-date=26 February 2014|newspaper=Union-Tribune San Diego|date=18 April 2005}} "Speed camps" and "Speed Training Manuals", which purport to provide fractional increases in maximum footspeed, are popular among budding professional athletes, and some sources estimate that 17–19% of speed can be trained.

Though good running form is useful in increasing speed, fast and slow runners have been shown to move their legs at nearly the same rate – it is the force exerted by the leg on the ground that separates fast sprinters from slow.Herper, Matthew. [https://archive.today/20130123132738/http://www.forbes.com/2004/05/14/cx_mh_0514running.html "What's The Human Speed Limit?"], Forbes.com, May 14, 2004, retrieved November 26, 2007. Top short-distance runners exert as much as four times their body weight in pressure on the running surface. For this reason, muscle mass in the legs, relative to total body weight, is a key factor in maximizing footspeed.

The record is 44.72 km/h (27.78 mph), measured between meter 60 and meter 80 of the 100 meters sprint at the 2009 World Championships in Athletics by Usain Bolt.{{citation |url=http://berlin.iaaf.org/mm/document/competitions/competition05/30/83/20090817081546_httppostedfile_wch09_m100_final_13529.pdf |title=International Association of Athletics Federations Biomechanical Research Project: Berlin 2009 |archive-url=https://web.archive.org/web/20140514050117/http://berlin.iaaf.org/mm/document/competitions/competition/05/30/83/20090817081546_httppostedfile_wch09_m100_final_13529.pdf |archive-date=2014-05-14 |access-date=2017-04-09 }}http://www.meathathletics.ie/devathletes/pdf/Biomechanics%20of%20Sprints.pdf {{Bare URL PDF|date=March 2022}} (Bolt's average speed over the course of this race was 37.578 km/h or 23.35 mph.)[https://engineeringsport.co.uk/2012/06/21/how-fast-is-usain-bolt/ How Fast Is Usain Bolt? Engineering Sport]

Compared to quadrupedal animals, humans are exceptionally capable of endurance, but incapable of great speed.[http://www.physorg.com/news95954919.html "Humans hot, sweaty, natural-born runners"], Physorg.com, April 16, 2007, retrieved November 27, 2007. Examples of animals with higher sprinting speeds include cheetahs which can attain short bursts of speed well over 100 km/h (62 mph),Kruszelnicki, Karl. [http://www.abc.net.au/science/k2/moments/gmis9911.htm "Fake Flies and Cheating Cheetahs"], Australian Broadcasting Corporation, 1999, retrieved November 27, 2007. the American quarter horse has topped 88 km/h (55 mph),Rinehart, Janet. [http://www.iqhra.com/], Iowa Quarter Horse Racing Association, retrieved November 27, 2007. greyhounds can reach 70 km/h (43 mph), and the Mongolian wild ass has been measured at 64 km/h (40 mph).American Museum of Natural History. [http://www.infoplease.com/ipa/A0004737.html "Speed of Animals"], Infoplease.com, retrieved November 27, 2007. The domestic cat may reach 48 km/h (30 mph).

In the 2023 Chicago Marathon, Kelvin Kiptum set a time of 2:00:35. That equates to an average speed above 20 km/h,(12.47mph) for two hours.{{Cite web |title=How fast was Kelvin Kiptum's men's marathon world record? Chicago Marathon 2023 race pace breakdown and split times |url=https://olympics.com/en/news/how-fast-was-kelvin-kiptums-world-record-2023-chicago-marathon-split-times}}

• Walking speed, the normal pace humans walk.

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• {{cite news |first=David |last=Stipp |title=All men can't jump |newspaper=Slate |url=http://www.slate.com/articles/sports/sports_nut/2012/06/long_distance_running_and_evolution_why_humans_can_outrun_horses_but_can_t_jump_higher_than_cats_.html |date=4 June 2012 |access-date=7 September 2012}}
• {{cite journal |last=Resnick |first=Brian |title=The animal kingdom's top marathoners |journal=Popular Mechanics |date=November 5, 2010 |url=http://www.popularmechanics.com/outdoors/sports/physics/animal-kingdom-top-marathon-runners |access-date=7 September 2012}}

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Category:Sport of athletics terminology

Category:Running

Category:Velocity