joer Loc: Colorado/Illinois

Most likely its the shutter speed.

I don't know Canon since I use Nikon. But if you can, set the shutter speed fast enough for the action and aperture for DOF and let the ISO float (auto ISO). A sharp noisy image is always better than a blurred noiseless image. You can always remove noise...can't remove blur.

E.L.. Shapiro Loc: Ottawa, Ontario Canada

It's important to note that the table I posted was written in the film era and was essentially intended for manual camera operation. Although the technology has changed, the basic optical, physical and functional photographic principles have not changed. The focal length data can be applied to a fixed or zoom lens and the shutter speeds relative to the direction of the action and the distance from the camera still holds true. My intention in posting the chart and outlining the theory was to give the OP or anyone else who is interested, some insight into action photography theory beyond the operation of a fully automatic camera system and thereby understanding how to manipulate the system to obtain the best results.

Of course, it is best to use the highest shutter speed to accommodate action coming form various directions and it is important consider depth of field as well. It is wise to consider shutter speed and aperture first and then adjust the ISO or allowing it to "float" That is an advantage of modern digital cameras with automatic ISO settings. Back in the film days the photographer had to select a film and processing method that would yield a workable all around exposure scenario for action shooting and of course, could not vary the ISO setting form one shot to the next on the same roll of film. As a result, many of the sports action shots we look back on, from the film days, are sharp and free of blur but grainy. Grain was the "noise" that film produced especially the high ISO varieties that were ofttimes push processed. Grainy images became well accepted and were part and parcel of many types of photojournalism.

Oh- and we didn't talk about electronic flash- yet! When electronic flash or SPEED-lights are the main source of exposure and the ambient light level is secondary or well below the flash exposure, the very short flash duration of most flash units will, in effect, freeze the action. Many speed-lights or portable electronic flash units average a flash duration of 1/1000 sec. or thereabout. Although the term "SPEEDLIGHT" is used a brand or model by the camera manufacturers, the term originally was generic in that electronic flash units have this intrinsic feature. When your flash units serves as a fill light source in ambient light conditions, the actual shutter speed still governs the action stopping capability of the camera. When using flash as a main or fill in source, the synchronization limitations of the camera's shutter has to be factored in as well.