Editing Running (section)

===Limits of speed===

[[Footspeed]], or sprint speed, is the maximum speed at which a human can run. It is affected by many factors, varies greatly throughout the population, and is important in athletics and many sports. Air resistance for top sprinters can take up to 5% of their energy.<ref name="r344">{{cite journal |last=Hill |first=A. V. |author-link=Archibald Vivian Hill |year=1928 |title=The air-resistance to a runner |journal=Proceedings of the Royal Society of London. Series B, Containing Papers of a Biological Character |publisher=The Royal Society |volume=102 |issue=718 |pages=380–385 |doi=10.1098/rspb.1928.0012 |issn=0950-1193 |doi-access=free}}</ref> 

The fastest human footspeed on record is {{cvt|44.7|km/h|m/s mph}}, seen during a 100-meter sprint (average speed between the 60th and the 80th meter) by [[Usain Bolt]].<ref>[http://berlin.iaaf.org/mm/document/competitions/competition/05/30/83/20090817081546_httppostedfile_wch09_m100_final_13529.pdf IAAF (International Association of Athletics Federations) Biomechanical Research Project: Berlin 2009.] {{webarchive|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 |date=14 May 2014 }}</ref>