NFL Draft: The 40-yard dash: Who’s responsible for it? Does it really matter to NFL teams? And why is it 40 yards?
http://blogs.mercurynews.com/collegesports/2014/05/05/nfl-draft-the-40-yard-dash-whos-responsible-for-it-does-it-really-matter-to-nfl-teams-and-why-is-it-40-yards/