system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is the 40-yard dash the magical number for gauging a football player's speed (as opposed to some other metric)?
gpt
While coaching Ohio State University Buckeyes football team in 1941, Paul Brown emphasized team quickness. One way to calculate this was for him to time his players covering a punt. At the time, the average punt went about 40 yards from the line of scrimmage and had a hang time of about 4.5 seconds. He would then time his players to see if they would be able to cover an average punt, or run a 40 yard dash in 4.5 seconds.  He continued with this strategy after becoming the head coach of the Cleveland Browns. The practice gained popularity from others as years went on and is the standard today.