[2][3] For purposes of measurement at the Combine, the run is made along the sideline from the front of the end zone to the 40-yard line, and for electronically timed 40-yard dashes, the runner is allowed to start when they wish, and a timer hand-starts the clock.
The fastest winning time, including reaction, was 5.2 (originally recorded as 51⁄5) seconds, first set by Rosa Grosse and later tied by Mary Carew twice.
[8] More recent examples include rugby union's Carlin Isles time of 4.22 at a Detroit Lions facility during a 2013 workout,[9] and Texas Tech's Jakeem Grant being hand-timed by a New Orleans Saints scout at 4.1 in 2016.
[10] In 2017, Olympic sprinter Christian Coleman ran a time of 4.12 seconds on turf in response to claims that NFL players are as fast as Usain Bolt.
[12] A year and a half after he retired from active competition, Usain Bolt ran a 4.22 in flat-soled shoes and a tracksuit at a promotional event for the Super Bowl in Atlanta, Georgia on February 2, 2019.