Fill Flash during races?

I shoot lots of mountain bike races, 5k runs, etc. Lots of these events are in the morning (9am starts for most). I typically like to shoot from a lower perspective looking up at the athletes, especially mountain bikers, to try and capture the pain/determination in their faces. I've just switched cameras and I'm still learning, but I am wondering if I need to use fill flash to bring out the details of the rider against a bright sky and underexposing the image to keep the sky from being washed out.

The example below shows what I'm talking about. Another question I have though is if it is even acceptable to use a fill flash as it might distract the athletes. Thoughts?

I would use flash for an image like this. Your other option is to expose for the shadows and let the background blow out. Sometimes that works and sometimes it doesn't. You can also try to selectively open up the shadows with Photoshop. I do that a lot. But I would use flash for a photo like this. It won't bother the riders as long as it's bright out. They'll see it but it won't affect them. If it was really dark and rainy, it might bother them. But I'd still use it. Usually they're so focused they won't care.

This photo was taken at Sea Otter, with flash.