Usain's top speed when he ran the 9.58 was 27.45 mph. So pretty close to 28. And some splits even say he hit 32 mph at one point. In a 40 yard distance he covers it in about 4.50 seconds. Note: This is after the gun whereas the clock starts in CJ's run AFTER he begins. Bolt's reaction time is usually about .18 seconds also. At the combine he'd probably run a 4.19 or so. Timed by hand he'd probably run a 4.10 or lower. But it still doesnt matter. Put CJ in blocks and start him at the gun and he wouldn't run a 4.5. Probably closer to a 4.7.