The Gipper could really throw a baseball!

Ronnie looked very capable in the scenes where he's pitching the ball(not referring to the stock footage). I don't think a stand-in was used and that he really was throwing the ball.

He was always very athletic, having been the captain of his college swim team and also played football.

And unlike some Presidents who throw like a girl and are booed after they throw out the first pitch, my favorite President always did everything like a real man!