I am not really surprised that you have some problems with runners. I have been shooting approaching objects, incl. waves and surfers. As RioRico pointed, pre-focus is the key.
In the case of really fast-approaching, I obtained my best shots with:
- a fast shutter speed (1/60 s or faster)
- manual focus, and
- Hi continuous shooting.
On the MF ring, I pre-focus the distance in advance. When the object approaches, I start shooting before the object is in focus and I gently follow (manually) the object with the focus ring. For that, I prefer to use MF lenses because the MF ring is much smoother, longer and more accurate. See also
https://www.pentaxforums.com/forums/pentax-beginners-corner-q/146443-manual-f...we-afraid.html.
Note that you do need to use a fast shutter speed. If you want to use a small aperture (eg f8), you will need some good sunlight or a fast lens.
I hope that the comment will help.