Do Lower Arm Slots Lessen Injury Risks For Pitchers?

Image credit: Chris Sale (Photo by Rich von Biberstein/Icon Sportswire via Getty Images)

In baseball, it’s common to hear coaches and fans describe pitchers by their “arm slot.”

Whether it’s overhand, three-quarters or sidearm, many believe arm slot is just a stylistic decision—something pitchers can and should change based on preference or performance. In fact, we have seen many prominent professional pitchers begin to adopt a lower slot recently, Paul Skenes and Jacob deGrom to name a few. 

However, new research suggests that arm slot is far less about personal choice and more about how the body moves. Specifically, how posture influences the throwing delivery.

A recent study looked at 87 elite college pitchers, all averaging around 86 mph on the radar gun. The goal? To understand how different arm slots influence stress on the shoulder and elbow—and whether certain slots come with biomechanical advantages.

What the researchers found was compelling: lower arm slots significantly reduce joint stress—both at the elbow and shoulder—without sacrificing velocity. But before we unpack what that means, let’s zoom out.

Why Arm Slot Isn’t What You Think

When most people think about a pitcher’s arm slot, they picture the angle of the forearm at release. But that angle doesn’t exist in a vacuum—it’s the result of a chain of movements happening earlier and deeper in the body.

The shoulder blade (scapula), for instance, doesn’t operate independently. It glides over the rib cage as the arm moves through the throwing motion. That means the position and shape of the rib cage—aka your posture—directly affects how the shoulder blade moves.

And if your scapula isn’t in an optimal position, it limits the range of motion and control you have over your throwing arm. In other words: The position of your trunk drives the path of your arm, not the other way around.

So when a pitcher throws from a low or sidearm slot, it’s not necessarily because they “chose” that slot. It’s often because their posture allows (or restricts) that movement pattern. Trying to change your arm slot without addressing your trunk and rib positioning is like trying to steer a car by turning the wheels while the axle is frozen—it doesn’t work.

What The Study Found

Here are the key insights from the research:

• Elbow Stress: Overhand pitchers experienced the highest elbow torque—6.7% of their body weight times body height—while sidearm pitchers had the lowest at 6.0%. That might sound like a small difference, but over thousands of throws, it adds up.

• Shoulder Stress: A similar trend showed up at the shoulder. Overhand pitchers had higher internal rotation torque (6.6%) compared to sidearm throwers (5.8%).

• Efficiency Wins: Sidearm pitchers were more torque-efficient. That means they generated more velocity per unit of stress on the joint—essentially getting more “bang for their buck.”

• Trunk Position at Release: Overhand pitchers showed significantly more lateral tilt (-23 degrees) and forward flexion (39 degrees), whereas sidearm pitchers were more upright, with only -12 degrees of lateral tilt and 26 degrees of forward flexion.

• Velocity: Despite these posture and torque differences, throwing velocity was statistically the same across all groups (avg. 86.3 mph).

So what’s the takeaway? The posture of the trunk—not just the arm—is the critical lever in the throwing motion.

The Postural Chain Reaction

Let’s break this down with a simple analogy.

Imagine your rib cage as the foundation of a building and your scapula as a sliding window mounted to it. If the foundation is tilted or unstable, the window won’t slide smoothly. Similarly, if the rib cage is rotated, extended or side-bent excessively, the scapula can’t properly guide the arm into a safe and powerful position.

This is why athletes who try to “change their arm slot” without addressing their trunk posture often end up feeling uncomfortable or lose velocity—or worse, get hurt. The scapula can only do what the rib cage allows.

The more side-bend and forward tilt an athlete adds at ball release (as overhand pitchers often do), the more extreme the shoulder positions become—and the more stress is placed on the joint. It’s not that sidearm throwing is inherently safer—it’s that the posture accompanying that slot allows for a more efficient load-sharing between the body and arm.

Should Pitchers Try A Lower Arm Slot?

That’s not the point.

The study doesn’t suggest that every pitcher should switch to a sidearm delivery. What it does suggest is that pitchers should stop treating arm slot as something that can be manually changed. Instead, they should focus on improving posture, scapular mobility and trunk control to naturally allow for an efficient and safe throwing path.

Strength and mobility work, movement assessments and throwing-specific drills should all be aimed at unlocking better movement from the inside out. When posture improves, arm slot may shift—but in a way that works with the body, not against it.

Final Thoughts

In the quest to throw harder and stay healthy, athletes and coaches often look for quick fixes—tweaks to mechanics, different grips, new drills. But the body doesn’t work that way. Throwing is a full-body movement, and the arm follows what the trunk and scapula make possible.