Canon EOS-1DX MARK II Settings Manual page 139

Set up steps
In [ISO speed settings] [Min. shutter spd.], you
can select the minimum shutter speed from
1/8000 sec. to 1 sec. in 1 step increments.
[AF tab 2]
From
[ISO speed settings]
Select
[Min. shutter spd.]
And choose a minimum
shutter speed
139