This story appears in the Feb. 21, 2011 issue of ESPN The Magazine.
FIVE SECONDS. That's more than enough time to finish the 40-yard dash for all but the biggest and slowest of those men asked to run it. For modern sports science, it's also plenty long enough to dissect the act into three phases. Blame Sun Tzu, who declared, "Speed is the essence of war." Blame 40 forefather Paul Brown, who took that maxim and ran (and ran). Most of all, blame NFL math, which tells us the difference between 4.5 and 4.4 isn't 0.1, but millions. Somewhere between Point A and Point B the 40 has grown much more significant than a simple wind sprint, offering hard-core coaches and casual fans alike a simple tool to analyze a complex sport and its specialized players. Break it down, though, and the 40 isn't so simple at all.