|SB-910. Shot at 1/32th power (approximately 1/17,000th of a second)|
1. There is plenty of available light (e.g. daytime)
2. You have a fast lens.
3. Your camera can shoot at high ISO without too much degradation of image quality.
In broad daylight, you should be able to get those kind of high shutter speeds even with a normal lens, and normal ISO. But once the light starts fading, then your choices are limited to managing with #2 (fast lens) and/or #3 (setting a higher ISO). It is for this reason you see sports shooters with those huge professional lenses that are designed to gather as much light as possible, and big camera bodies that are designed to shoot at high ISO speed and still give excellent image quality.