Good setup for ruuners with 40D, 17-55 f2.8 lens

40D, 17-55 2.8 lens, speedlite 580 II:
Any advice on a useful setup for shooting runners on course, and at finish, about 10AM.
Would Tv at 1/250, flash stop the action?
Would high speed sync give better results?

Thanks

Set it at AV 2.8, ISO (whatever you need to hit at a minimum 1/500th). If you want to use flash use HSS. You'll burn though batteries. On course basically the same thing if thats the only lens you have. I shoot runners on course with out a flash and I typically strobe the finish line with alien bees. I used flash when i started but would run though batteries.

I shot one for a non-profit a few weekends ago with a 20D at Av f/5.6 at the start and finish line. AI servo. My shutter speed was around 1/500 or faster as I recall. The sun was occasionally behind a cloud. There was no motion blur. I wouldn't even think of using a flash. Maybe a marathon spreads them out more, but they're coming in bunches at the peak of a 5k. The flash wouldn't recycle fast enough and I'd have no time to change batteries. Truth to tell, finishers are not generally looking their best at the end of a race. If they want anything at all, it's a doc shot with the finishing time in it. Glamour photography is not on their minds. One guy who didn't race had the idea of handing his wife a bouquet when she crossed the finish line. She looked at him like, "What? You expect me to carry those?!"

At the start line, I used an 80-200 to give me a little distance from the runners so I could skedaddle out of the way. If you're standing in the middle of the street, the ones at the front of the pack will see you and run around you. But the ones farther back will bowl you right over. Think of a cattle stampede.

^as a runner, please don't stand in the middle of the course. I'm paying good money to not have to run around people. Unless you're there as the official event photographer and you get explicit permission from the organizer, I wouldn't even consider it.

Never stand in the runners path. Always stand off to the side of the path the runners are running. I always sit to either side of the chute about 15 feet back from the finish, but I'm also the official photographer for the races. I haven't been run over yet, but have had a few close calls. I usually move the barricade used to make the chute back to make a little indention for myself.

If the finish line is wide enough you could stand ~15-20 feet back in the dead center of the chute, but that would only be for really wide finish lines and longer distance races. I would only do this for a half-marathon and up. All the other size races you'll see a few large groups of people finishing at the same time and some of them like to sprint ahead. But I would not recommend this unless your a race veteran.