Thank you, all, for your comments.
Tommie, I was shooting AFC at 11 fps. Where the EXIF shows 200mm, this was the Fuji 200/2; where the dedicated 1.4 t/c was used the EXIF shows 280mm. The light for the hurdles was good, but later on became overcast and we had a couple of rain showers.
Peter, you are right, the AF of the X-T3 is a major improvement over that of its predecessors. I no longer feel at a disadvantage to a DSLR user when shooting sports.
Ann, the sand does give some good opportunities for photos, unlike the foam mats used by the pole vaulters!