Please be careful if you're thinking of using flash. If it is a sporting event or a competition, flash is generally not allowed as it may blind or distract the competitors.
Another thing about using flash to reduce blur/movement is the existing lights there. If you're shooting in a bright light or even low daylight suitation, you may still get blur or movement images. Example:
Camera setting: f.5.6 speed 125/100
Existing lights: f.5.6 at speed 125/100
If you are allowed to use flash, make sure that you use smaller f. and the fastest shutter speed which can sync with your flash. This will help to reduce the existing light but the down side is that the background may be dark. Some trial and error will be needed to get the right brightness for the b/g and still freeze your frame. If you can't use flash, than a fast lens will come in handy. Use faster shutter speed, open up your f. and bum up your iso.
Hope it helps.