I applaud you for thinking outside the box, but unless those runners were breaking the sound barrier, you probably didn't need more than 1/400 shutter speed (or somewhere around there). If that were the case, then you could down the ISO to 250 and have the same exposure.
I don't shoot a ton of sports, so I could be missing something here. But I do shoot birds in flight, which I believe move much more quickly than humans on foot.
Either way, very nice shot that accomplished exactly what you wanted! The DOF and your use of narrow aperture is spot on.