In today's Journal, you wrote that Adrian Peterson "recorded a 4.38 second 40-yard dash at the 2007 NFL combine, a time that roughly converts to about 11.98 seconds for 100 meters."
That statement is simply not true. A 4.38 40-yard dash time doesn't convert to 11.98 seconds. If someone ran 100 meters at the same pace as a 4.38 40 yard dash, they would run 11.98 seconds but that's not nearly the same thing as "converts to" as it ignores the fact that the first three 10 meter segments of a 100 meter dash are by far the slowest.
40 yards is 36.576 meters. When Usain Bolt ran his world record of 9.69 at the Beijing Olympics, his opening four 10 meter splits have been estimated to have taken 1.85, 1.02, .91 seconds and .87 seconds according to speedendurance.com, meaning that he passed 30 meters in 3.78 seconds and 40 meters in 4.65 seconds. Assuming he ran the same speed between 30 and 40 meters (which isn't true as he's still accelerating), he would have passed 40 yards or 36.576 meters in 4.44 seconds - some .06 seconds behind the 4.38 time recorded by Peterson. In reality, because he's still accelerating, Bolt might have been a tiny bit slower than that.
Admittedly, since NFL 40 times don't use fully automatic timing (FAT) on the start (which adds .24 seconds) and the timer reacts to the runner starting (adding even more time), NFL 40 times are very generous to the runner and in reality much faster than what would be recorded in a track and field race. In reality, Peterson would be behind Bolt at 40 yards, but Peterson's is much better than an 11.98 100 meter sprinter.
Since there is no FAT at the start and the starter reacts to the runner and not vice versa, comparing 40 yard times really isn't a scientific process at all, but consider this.
The Oakland Raiders Jacoby Ford was a 10.01 guy in college. His 40 yard time was 4.28.
Jeff Demps, who won 4 individual NCAA titles for Florida and is a 9.96 man and ran on America's 4 x 100 American record team this summer in London, recorded a best 40-yard dash time of 4.18 seconds in 2012 before signing with the Patriots (http://www.nfldraftscout.com/ratings/dsprofile.php?pyid=82451&draftyear=2012&genpos=RB).
Peterson isn't quite in their league but he does have some bragging rights.
Justin Gatlin, who once had a drug induced world record in the 100 meters and who won the bronze at this summer's Olympics, ran a 40-yard dash during an NFL tryout while serving his doping ban in 2008. His time? 4.42 seconds (http://www.letsrun.com/forum/flat_read.php?thread=2423085).