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The 40-yard dash is a sprint covering 40 yards (36.58 m). It is primarily run to evaluate the speed of American football players by scouts, particularly for the NFL Draft but also for collegiate recruiting. A player's recorded time can have a heavy impact on his prospects in college or professional football. This was traditionally only true for the "skill" positions such as running back, wide receiver, and defensive back, although now a fast 40-yard dash time is considered important for almost every position. The 40-yard dash is not an official race in track and field athletics and is not an IAAF-recognized event.
The origin of timing football players for 40 yards comes from the average distance of a punt and the time it takes to reach that distance. Punts average around 40 yards in distance from the line of scrimmage, and the hangtime (time of flight) averages approximately 4.5 seconds. Therefore, if a coach knows that a player runs 40 yards in 4.5 seconds, he will be able to leave the line of scrimmage when a punt is kicked, and reach at the point where the ball comes down just as it arrives.
Timing method and track comparisons 
In terms of judging a person's speed, the best method of timing is through lasers which start and stop the times when passed through. A laser start (from a stationary position) is more accurate for measuring pure speed as it does not register a runner's reaction time. However, the method of timing a 40-yard dash can affect the accuracy by as much 0.5 seconds (with the manual stopwatch method). The National Football League (NFL) did not begin using partial electronic timing (started by hand, stopped electronically) at the NFL Scouting Combine until 1990.
In track and field races, the runner must react to the starting gun, which takes approximately 0.24 seconds, based on FAT timing. For electronically timed 40-yard dashes, the runner is allowed to start when he wishes, and a timer hand-starts the clock. This aspect means that comparisons with track times are impossible given that a reaction time is not factored in. Furthermore, the use of hand-timing in the 40-yard dash can considerably alter a runner's time; the methods are not comparable to the rigorous electronic timing used in track and field.
This is a list of the official 40-yard dash results of 4.30 seconds or better recorded at the NFL Scouting combine since 1999, the first year electronic timing was implemented at the NFL Scouting Combine. Prior to 1999, 40 yard dash times were somewhat unreliable and often prone to exaggeration.
In 1986, Auburn's Bo Jackson ran the fastest 40 yard dash at an NFL combine, with a reported time of 4.12. This time was scrutinized, but a time of 4.18 run by Jackson within the same week added some support to the legitimacy of the times.  Deion Sanders ran a 4.27-second 40-yard dash in 1989. In 2013, on Utah Utes pro day Wide Receiver Reggie Dunn ran a 4.26 forty yard dash. He was not selected in the 2013 NFL draft but was later signed by the Pittsburgh Steelers.He has also run the Forty yard dash at a time of 4.22.
|4.24||Chris Johnson||5 ft 11 in (180 cm)||197 lb (89 kg)||Running back||2008||#24 overall by Tennessee Titans|
|4.25||Darrius Heyward-Bey||6 ft 2 in (188 cm)||210 lb (95 kg)||Wide receiver||2009||#7 overall by Oakland Raiders|
|4.27||Stanford Routt||6 ft 2 in (188 cm)||193 lb (88 kg)||Cornerback||2005||#38 overall by Oakland Raiders|
|4.27||Marquise Goodwin||5 ft 9 in (175 cm)||170 lb (77 kg)||Wide receiver||2013||#78 overall by Buffalo Bills|
|4.28||Anthony Williams||6 ft 1 in (185 cm)||176 lb (80 kg)||Cornerback||2011||#81 overall by Oakland Raiders|
|4.28||Champ Bailey||6 ft 0 in (183 cm)||184 lb (83 kg)||Cornerback||1999||#7 overall by Washington Redskins|
|4.28||Jerome Mathis||5 ft 11 in (180 cm)||181 lb (82 kg)||Wide receiver||2005||#114 overall by Houston Texans|
|4.28||Jacoby Ford||5 ft 8 in (173 cm)||190 lb (86 kg)||Wide receiver||2010||#108 overall by Oakland Raiders|
|4.29||Josh Robinson||5 ft 11 in (180 cm)||200 lb (91 kg)||Cornerback||2012||#66 overall by Minnesota Vikings|
|4.29||Trindon Holliday||5 ft 5 in (165 cm)||155 lb (70 kg)||Wide receiver||2010||#197 overall by Houston Texans|
|4.29||Fabian Washington||5 ft 11 in (180 cm)||188 lb (85 kg)||Cornerback||2005||#23 overall by Oakland Raiders|
|4.29||Dominique Rodgers-Cromartie||6 ft 2 in (188 cm)||184 lb (83 kg)||Cornerback||2008||#16 overall by the Arizona Cardinals|
|4.30||Yamon Figurs||5 ft 11 in (180 cm)||174 lb (79 kg)||Wide receiver||2007||#74 overall by Baltimore Ravens|
|4.30||Darrent Williams||5 ft 9 in (175 cm)||176 lb (80 kg)||Cornerback||2005||#56 overall by Denver Broncos|
|4.30||Tye Hill||5 ft 10 in (178 cm)||185 lb (84 kg)||Cornerback||2006||#15 overall by St. Louis Rams|
- "Top Performers 2006-2011". 16 July 2011.
- "Officially, Van Dyke is combine’s fastest player". 1 Mar 2011.
- Based on Cooney, Frank (23 February 2008). "Combine 40-yard times -- Nothing is official". The Sports Xchange., plus updates.
- "With 40-yard dash times, nothing's quite 'official'". 24 Feb 2008.
- Hessler, Warner (April 23, 1989). "NFL General Managers Moan About Another Diluted Draft". Daily Press. Retrieved 2012-03-01.
- "Darrius Heyward-Bey - WR - Maryland - 2009 NFL Combine Results". NFL Combine Results.