I guess TC is not recommendable for action photography
When you use a 1.4x teleconverter, one of the costs you pay is the "loss" of one f/stop of maximum aperture. This makes it harder to focus (either for you or the camera's AF system). If you were already shooting wide-open to freeze action, it also means that you'll need to keep the shutter open twice as long.
For us amateurs, getting closer to the action is not always an option, and fast long telephoto lenses are large, heavy, and expensive. So while a teleconverter may not be an ideal solution, using one is often a reasonable way to get some extra reach without breaking the bank or your back.
One of the biggest mistakes a photographer can make is to look at the real world and cling to the vain hope that next time his film will somehow bear a closer resemblance to it. - Galen Rowell