found this on Bolt's 2009 WC 100m
Usain Bolt 100 meter Splits
Table 1: Usain Bolt estimated 100 meter splits at 2009 World Championships.
Above are the 100m splits of Usain Bolt from Berlin at the 2009 World Championships. At 30m he is about 3.78 and at 40 he was estimated to be 4.64. The fastest 40m ever run is by Usain Bolt, so while at 30m Michael Green may have had a step (actually a toe) on Usain, 6.6 meters later he was caught and passed slightly. No to get too complicated with the mathematics, each step the athlete is accelerating faster and faster, but not perfectly, so we can only estimate what Usain bolt was doing based on calculations. The most logical approach is to use the data from Berlin and create a model that has a line similar to one of best fit. Even the most advanced calculations are only going to be an estimate, and we will be only rounding to the nearest hundredth. Based on the data, it’s estimated that Bolt ran a 3.63 for his 30m minus the reaction time. Now the real question is what was he at 40 yards exactly. Splits every ten meters appear linear, but even the small segment of ten meters still has a curve. Even if one calculates the time at 36.6 meters it’s still an estimate, and most conclude 0.556 to 0.582 is realistic based on the time segment from 30m to 40m.
Adding 0.571 to the 3.63 time segment to get a 40 yard dash running time is about 4.20, and that includes no reaction time subtraction of the timer from the combine. While it hard to know what the true reaction time of the timer is, conservative estimate is about 4.10 by removing 0.1 or a tenth. If the timing was completely hand time, meaning a stop watch, removing the accepted 0.24 from 4.20 would equate to about 3.96, or a sub 4, a level no football player would match.