The problem is with sports, if you have it turned on it affects the FPS and when the camera takes a shot. So it's recommended for getting the shot especially if you use 10fps, to have it turned off. There's a short thread about it on TPF somewhere here that I think I started about the Flicker.
While the manual reports that this could be a problem, I've not yet experienced it. Ive been shooting indoor sports in buildings with known cycling lights, at 10 fps, and not lost frame rate or experienced any hesitation.
I suspect that that slower shutter speeds you could run into it, but at 1/500+ it hasnt slowed my camera down at all.
If you think about it, you're shooting ten frames per second. The light cycles 60 times per second. That means that it just had to choose the brightest 10/60 cycles, which, in my experience, hasn't slowed my frame rate at all.