Canon EOS-1D X Mark III Af Setting Manualbook page 22

If there are situations where the subject moves away from
the AF points for an extended period, try manually setting
the [Tracking sensitivity] parameter to [-2], for better
performance.
[Case 2]
Photo
Try selecting [Case 2] when shooting a track and field event.
Runners closer to the camera will pass between the camera
and the target runner targeted with the AF point, with
this setting the camera will ignore the closer runner and it
will be possible to continuously focus on the target runner.
22 22