[Tru_in_Blu]

"Warming up a pitcher" apparently means that one of the participants is throwing underhand, as in the pitching delivery.

Last year's case book said that if a non-adult did not have the approved helmet/mask/throat protector, the catcher may not warm up the pitcher. The two players may play catch.

It has nothing to do with whether the catcher is upright, squatting, or on 1 or both knees.