What Causes a Curveball to Curve?

Strike three and the batter is out. You have just struck out another batter with your curveball. But in order to throw a curveball correctly, you need to know what makes a curveball curve. You will need to practice the pitch often to get your grip, mechanics and release just right. And knowing the physics behind a curveball will help you become an even better pitcher.

  1. Grip

    • A proper grip on the baseball is important to making it curve. If you try holding the ball with the seams facing the wrong way or with your fingers in the wrong position, the ball is not going to curve. According to former Chicago Cubs pitching professional Steven Ellis, you should place your middle finger on the inside seam. Basically this means your middle finger should run along the rounder part of the red seams. Your index finger should be lightly placed next to your middle finger but should be barely touching the ball, if at all.

    Mechanics

    • Much like the grip, your mechanics and body motion also have a lot to do with making a baseball curve. You should try to throw the curveball in the same way as a fastball, except you will want to make your stride a few inches shorter. This allows you more time to put the proper spin on the ball. Your arm should be an L-shape when throwing. Your elbow should be bent and even with or slightly above your throwing shoulder. Your arm speed should also be about the same as your fastball. This not only helps you build enough velocity for the curveball, but it also will not tip off the batter as to which pitch you are throwing.

    Release

    • How you release the baseball is another crucial factor to making it curve. While your mechanics may be similar to throwing a fastball, your release will be much different. Instead of throwing the ball out in front of your body, as with a fastball, release the ball from the side with your wrist hooked. After the release, your hand should pull down in front of your body. You will essentially be aiming the ball away from the plate toward the batter instead of over the plate as with a fastball. The tighter the spin you give the ball, the more drop it will have and the less time it will spend hanging in the air.

    Physics

    • After you have thrown a baseball, physics takes over. How these natural forces take over is based on how you have thrown the ball. A properly thrown curveball will have spin that allows the air pressure under the ball to flow faster than the air pressure above it. Thus, the ball will break or dive near the end of its trajectory. The stitching on the ball will gather up air as it rotates and also create higher air pressure on one side of the ball, causing it to break.