Why some pros aim low on warm up strokes

On video tapes, some top US pros like Mizerak, as well as most of the
great Filipino stars like Bustamante are near the bottom of the cue
ball when rehearsing the final delivery stroke. They do it on every
shot as if they were about to draw the ball -- even when they intend to
hit center ball or apply top spin.

Asking around at a tournament I heard two interesting reasons given
from various players (even some who don't aim this way):

-- Rehearsing low when grooving the aiming line to the object ball
enables some players to see more of the cue ball and thus (for them)
more of the relationship between cue ball and object ball.

-- For some players' vision, since the very bottom of the cue ball
contacts only a small point on the cloth, it's easier to guarantee that
you're truly on the vertical centerline of the cueball during initial
sighting of CB to OB aiming line.

Hope this gives some insight to others who like me, were puzzled by
certain players always starting their aiming from very low on the cue
ball. I've subsequently experimented with this on difficult shots and
it has improved my pocketing a great deal in spite of feeling odd at
first. I'm working to do it now on every shot to further ingrain the
habit, since for my vision, it has proven helpful.

-- Carlton