Film speed is the level of sensitivity that the film has to light. The higher the film number the more sensitive the film and the less light needed. The only draw back is the higher the film speed the grainier the image will become. For fencing photography, an 800 speed film gives a good balance. The next factor in dealing with low lighting is aperture.
Aperture is simply the hole in the camera that lets light in.
The aperture opening can be increased or decreased in size by changing the F-Stop. Normally not a bad effect for fencing action shots. With 800 speed film, the optimum F-Stop is f 4 or f 2.8. The aperture setting must be considered along with shutter speed. Shutter speed describes how quickly the shutter opens and closes exposing the film to a flash of light.