I take photos each Friday night at the local athletics meet here in Perth. It's always a great way to spend an evening, and the challenges of the lighting keep me on my toes!
I used to earn a few extra bucks taking track, cross country and road race pictures. I know the challenges involved. Very nice job on these! Being a former sprinter myself, I especially like the last one of the man coming out of the blocks.
They're all taken with a Tamron 70-200 f2.8. I was given it to review a while back, and it outperformed the Nikon version so much that I kept it (well, bought it).