Timing method and track comparisons[edit]

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, this method of timing a 40-yard dash can affect the accuracy by as much as 0.5 seconds with the manual stopwatch method.


The National Football League (NFL) did not begin using partial electronic timing (i.e. started by hand, stopped electronically) at the NFL Scouting Combine until 1999.^[2][3] For purposes of measurement at the Combine, the run is made along the lower sideline from the 40 yard-line to the end zone, which has built-in rundown space, and for electronically timed 40-yard dashes, the runner is allowed to start when they wish, and a timer hand-starts the clock.


In contrast, track and field races have the runner react to a starting gun, which takes approximately 0.24 second (based on FAT timing); further to this, IAAF rules state any runner with a reaction time of less than 0.1 second is subject to disqualification.


This aspect means that comparisons with track times are essentially impossible given that a reaction time is not factored in, and 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.^[4]


For example, Jacoby Ford, who ran 4.28 s in the 2010 NFL Combine, had a collegiate best of 6.51 s in the 60-meter dash (outside the top-40 of the all-time lists).^[4]