The 40-yard dash is a sprint covering . It is primarily run to evaluate the speed and acceleration 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 race. 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 player can run 40 yards in 4.5 seconds, he will be able to leave the line of scrimmage when a punt is kicked, and reach 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, 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. 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 for world class male sprinters takes approximately 0.11 to 0.15 of a second. 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