A Look Inside an Infielder’s Varying Arm Slots

It’s no secret or surprise that infielders need to throw from a variety of arm slots in order to be effective. The ability to throw from different arm slots saves precious time while attempting to record an out. Before we dive into arm slots, it’s important to distinguish the difference between the terms “arm slot” and “arm action.” So many times, these terms get tossed around almost interchangeably, but they are two different terms.

The term arm slot refers to the angle from which the infielder releases the ball, while arm action refers to the motion of the arm in the throwing process.

On the surface, throwing from different angles looks like the arm action changes. In reality the arm action mostly remains the same but the arm slot changes.

How does the arm slot change?

To change the arm slot, the infielder must change their posture. You read that correctly. Your posture dictates your arm slot. You change your posture by adjusting the angle of your spine in relation to the ground.

Why does your posture change your arm slot?

When you throw using the proper arm action and form, there is a natural 90 degree angle that forms. This angle is made up of your spine being the vertical line and the horizontal line is your shoulders extended out to your throwing elbow. In theory, your shoulders rotate around your spine when you throw. Now this isn’t exactly biomechanically correct, but for the sake of simplicity and concept understanding we’ll go with it. This 90 degree angle remains the same no matter the arm slot you use: over the top, 3/4, side arm, or underneath. What changes is the angle of your spine in relation to the ground. The more upright the angle of the spine is, the more over the top the arm slot. As that spine angle gets closer to horizontal to the ground the arm slot moves closer to a “submarine” or underneath arm slot.

How does your arm slot affect ball flight?

Your varying arm slots will have different effects on the ball flight. Each arm slot will generate a certain type of backspin on the baseball. Before we dive into affects on ball flight, let’s assume a few things: (1) you consistently throw with a 4 seam grip and (2) your hand is consistently behind the ball when you release. These two assumptions give the ball it’s truest flight in each arm slot. Not having a 4 seam grip or cutting the ball on release with your hand will cause the ball to run, slide, dip and any other adjective to describe ball flight.

We use a clock to help categorize the arm slot and the subsequent movement it gives the ball. The closer the arm slot gets to 12, the truer the backspin (12-6) and, therefore, the truer the ball flight. As the arm slot approaches 3, the ball will have a side spin (3 to 9) and the ball will have more horizontal movement to the arm side. As the arm slot approaches 6, the ball will have an up spin (6-12) and the ball will have more of a vertical movement down to the ground.

Why would we want to change our arm slot?

The time available to record an out is limited, and as such, we aren’t always able to use our most comfortable or natural arm slot. Changing arm slots will save precious time and improve the potential to record the out. One phrase that you may have heard before is, “throw it from where you catch it.” This cue refers to the level in which you receive the ball. If you catch it low, throw it from a low arm slot. If you catch it high, throw it from a high arm slot. Arm slot versatility allows this to happen.

Another reason to change arm slots is to counteract our momentum for an easier release that allows us to maximize our velocity. Fielding the ball on the move or on the run is a necessity at times. In these situations, we don’t have the luxury of stopping to set our feet and throw using our natural arm slot. Changing our arm slot in these situations maximizes our arm strength given our momentum in the direction we’re moving. I don’t believe there is a specific arm slot for specific directions we’re moving. Choosing the best arm slot will be based on the individual’s skill and comfort. Getting comfortable using these various arm slots will help us understand how our arm responds and will become a deciding factor in which one we use.

Mastering a variety of arm slots

The best way to get comfortable using a variety of arm slots is to, simply put, use a variety of arm slots. Assigning a throwing task, as described in my previous post here, is a good first step in a progression that allows for practice in a controlled environment. Below is a sample progression for arm slot mastery:

  1. Stationary mixed arm slots throwing task
    • After receiving the ball, set your feet, establishing the posture you’d like to throw from with your spine angle, then return throw from your chosen arm slot. Vary your arm slot with each return throw.
  2. Momentum throws
    • After receiving the ball, move in one direction and throw from the appropriate arm slot. Every time you receive the ball, move in a different direction to throw the ball back: to your target, away from your target, laterally, and diagonally.
  3. Controlled action throws
    • Utilize different arm slots across different play demands from a fungo (double play feeds, double play pivots, relay throws, etc.).
  4. Game speed throws
    • Use different arm slots in game action.

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