Arm action varies depending on the player and the position they play. The idea is to be fluid and demonstrate a continuous arm action through your target, regardless of your situation. Your aim should be aligned with your step, shoulders, and hips.
Your hand separation is also necessary. Separate your hands (baseball from glove) by rotating your throwing hand’s thumb down in a circular motion until your thumb is pointed to the sky.
Finally, instead of decelerating your arm action, concentrate on accelerating it through your target.
Try the figure 8 drill to improve your arm motion. While accelerating past the target, this drill helps you maintain good fluid movement and continuous arm action. Move the ball in a figure 8 motion with your throwing hand a few times. With your arm extended in front of your body, perform this exercise. Bring the baseball up to the sky, step, and throw in a regular motion while you finish the lower portion of the figure 8 activity with your throwing arm. Maintain the momentum created by the figure 8 motion and speed to the finish line.
Remember that good arm movement can aid in the development of an accurate and powerful baseball throw.