Gary Fong photographed this sequence of a pole vaulter using the Sony a9. The camera was set on MANUAL mode, ISO 6400 wide open with a 70-200mm f2.8 G Master lens wide open to f2.8. Shutter speed was set to 1/2500 sec to freeze the motion. Note that there is no image blackout while shooting.
The “blinking” of the focus boxes is the shutter going off. You can also see the images during playback.