The real culprit for digital cameras is shutter lag. Many less expensive cameras can take up to a second after you have pressed the button for the picture to actually take. With the unpredictable requirements of an action shot, these can leave you with foggy and blurred pictures. You can cut down on some shutter lag by depressing the button on the camera halfway so that some of the wait is reduced.
Another way to overcome this handicap is by actually moving the camera as the shot develops. By following through with the direction of the movement you are trying to capture, you can end up with a lovely shot. This technique is called panning. To properly do this you must begin take the shot and follow through for up to two seconds. The image result will be of a crisply focused subject and a blurred background.