Here is a good article by the USOC about NFL 40 timing. It is from last year and mentions Jerome Mathis. http://www.usoc.org/11611_32384.htm

That doesn't make sense. There are about 109 yards in a 100 meter race. If Johnson needed 9.79 seconds to finish and 4.38 to go the initial 40 yards, Ben only had 5.41 seconds to go the final 69 yards. 69 yards = 63 meters. How can Johnson travel the first 60 meters in 6.37, but the last 63 in 5.41? Johnsons 50 meter speed is 20.26 mph. A 19 mph average speed would cover 40 yards in about a 4.30. Johnson was going at least that fast in Seoul.

Maybe I've gotten lost in the numbers, but is it possible he simply sped up? I mean, just the natural ability to run faster with competition. I might be missing the entire question there, but with 'roids in his system, he may have just turned on the jets when he realized a couple guys were staying with him during the first 4/10ths of the race.

Well I think we can all agree it should take less time to go the last half of 100m right? So if he is doped up on roids, maybe he was still accelerating throughout the last half as well. So on top of the amount of ground he covered in the first half, there was the amount that he gained by accelerating even more during the last half...sorry about the vague response, but due to a continuation of acceleration it seems very feasible...

That sounds a lot more scientific than my conclusion of "he sped up". I've never been much for math...

I'm not sure if this is what you are asking, but the 2nd half of a spring like the 100m would be faster than the first half because you are at or near your top speed, plus you don't have to react to a starting gun.

I'm sure he did speed up during the race. But averaging 18.7 mph over the first 40 yards, then 26 mph over the last 69 yards? Still it's an apples & oranges comparison, since the Olympians are timed beginning at the starter's gun, while the NFL begins timing on movement. I'm certain that a Ben Johnson or Carl Lewis could have run under a 4.20 40 if timed with the NFL method.

Yep, it's called acceleration. Johnson was 'roided up so he could have the strength to maintain or even increase his top speed. For example, in ninth grade...I went out for track and ran 5.4 -50 yards (hand-timed)...ran close to 12 seconds in 100 . only weighed 135 lbs.so I wasn't too strong.

The remarkable runners are the ones that run the 200 meters.....like Johnson from Baylor. To maintain that speed for that distance is awe -inspiring.

I wonder what the average distance is for peak speed. What you seem to be doing though by comparing those averages seems to be a mistake in itself - Considering the acceleration, there's no way you can compare the first 10 yards of the 40 with the last 10 yards of the 40. Breaking it up and trying to compare the averages just seems to ask for some weird numbers. I'm sure if you saw an entire break down of every 5 or 10 yard segment, the end of the first 40 yards would be much closer to 26 mph than 18, which would shed a little light on the whole thing.

When world class sprinters run the 100 - they accelerate smoothly up to 27 mph at around 30 to 40 meters then hold that speed through the finish.