alteration of the pitching motion

[UmpJM]

Bruno,

The way I think of that phrase is that the pitcher can't start to do one thing and then change to do something else.

For example, a RHP lifts his stride leg to balance as he would in delivering a pitch or making a pick-off to 3B, but then suddenly turns and steps & throws to 1B. He illegally "altered" what he was doing.

If he stops, he has violated the "without interruption" clause.

JM

[johnnyg08]

Sometimes you'll see a start/stop balk called which can also apply to the "w/o interruption" clause.