Experimenting with "panning"
Panning is the capturing of motion while following the moving object so that the background is blurry, but you can see the moving object.
Shutter speed is crucial here. Here on this bright sunny day, I was able to use ISO 100, and after experimenting, I found a shutter speed of about a half a second to be the sweet spot! With those two down (shutter speed and ISO), I used my light meter to come up with f/29.
We love to run around on this Boulder field in Nederland. Our Golden Retriever runs, Satori runs, and my DH I try to get to run.