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The arm slot debate has been going on for as long as pitching coaches have existed. Some swear by high three-quarters, others preach sidearm, and everyone has an opinion about what's safest and what produces the most velocity. But a 2023 study by Manzi and colleagues suggests that if we look at arm slot as the sole factor affecting stress and performance, we'll be left with more confusion than clarity. This study compared 130 high school pitchers and 288 professional pitchers using high-quality motion capture, making it one of the more powerful datasets we have on this topic. What they found was that the relationship between arm slot and joint torque is completely different depending on skill level. For professional pitchers, a more sidearm approach was associated with reduced elbow varus torque and shoulder internal rotation torque. For high school pitchers, the same lower slot was associated with increased elbow flexion torque. Same slot, opposite outcomes. The larger implication here isn't about arm slot at all. It's about the timing of segmental movement and its effect on energy transfer.
The researchers analyzed kinematic and kinetic data from both cohorts, comparing how arm slot position at ball release related to trunk positioning, shoulder abduction, and joint torques. High school pitchers in this study, on average, tended to exhibit a more overhand arm slot at ball release compared to their professional counterparts. For both groups, a more overhand style was associated with greater shoulder abduction and more lateral trunk flexion around the moment of ball release. This makes sense mechanically. To get the arm up higher, you have to tilt the trunk more.
Where things got interesting was in the torque relationships. Professional pitchers utilizing a more sidearm approach demonstrated a potentially delayed timing of maximum upper trunk angular velocity compared to pros with an overhand style. That delay in trunk rotation appeared to be protective. In the professional group, lower arm slots correlated with lower elbow varus torque and lower shoulder internal rotation torque. But in the high school group, lower arm slots correlated with higher elbow flexion torque. The same mechanical position produced opposite stress profiles depending on who was doing it.
The study also found that arm slot position is fundamentally linked with shoulder abduction and lateral trunk tilt. You can't change one without affecting the others. This interconnection is why isolated cueing of arm slot often fails. The arm doesn't operate independently. It's at the mercy of the rotational path taken by the torso.
This study provides more context to an idea that has been building across the research for years: the arm is really a passenger, not a driver. What the torso does before ball release dictates where the arm ends up. A 2025 study on elite college pitchers found that for every 10 degrees of decrease in arm slot, elbow varus torque decreased by approximately 4.23 Nm, while torque efficiency increased, all without any reduction in velocity. But again, this was in skilled throwers who had developed the coordination patterns to support that slot.
The professional versus high school comparison becomes clearer when we look at research on rotational kinematics. A 2018 study found that professional pitchers generate more velocity with less relative elbow torque by using greater trunk and pelvis rotation. High school pitchers who threw harder in that study also produced the highest elbow torque relative to body size. The professionals had learned to time and sequence their hips and trunk so the arm simply transferred energy rather than creating it. When that sequencing breaks down, the arm picks up the slack.
Research on trunk-pelvis timing reinforces this point. A 2025 study on Australian pitchers found that later trunk rotation relative to the pelvis was linked to higher ball velocity. This finding aligns with what the arm slot study showed in professionals: those with lower slots demonstrated delayed trunk rotation, and that delay appeared to be protective.
Pelvic-trunk coordination research adds another layer. A 2025 study found that greater separation between pelvic and trunk rotation from foot contact to maximum external rotation was positively correlated with velocity (r = 0.74). The ability to create and then release separation is what allows energy to flow efficiently through the chain. Without it, the arm has to generate force on its own.
Even the research on elbow flexion tells a similar story. A 2025 study found that high school pitchers begin the throw more flexed at the elbow and never reach the same extension as professionals. The authors noted that the arm often reflects what the trunk does before it. Core strength research supports this as well. A 2024 study found that glove-side oblique strength correlated with both pelvis and trunk rotation velocity, without increases in joint torque. Athletes with stronger cores rotated faster and more efficiently.
The practical takeaway here is straightforward: stop coaching arm slot in isolation. The arm ends up where the torso puts it. Trying to force a specific slot without addressing the trunk positioning and timing that creates it is likely to produce compensations rather than improvements. For high school pitchers especially, the priority should be developing coordination patterns that allow energy to transfer through the trunk before the arm accelerates. That means training sequencing, not positions.
Programming should emphasize drills that teach the pelvis to rotate first, then the trunk, while maintaining stability through the lumbopelvic region. Resisted trunk-pelvis dissociation work, rotational medicine ball throws with an emphasis on separation, and single-leg stability drills under rotational challenge can all help reinforce the patterns that distinguish efficient throwers from inefficient ones. Core strength, particularly the obliques on the glove side, should be a priority.
For athletes who naturally fall into a lower arm slot, the goal isn't to change it. The goal is to ensure the trunk timing and sequencing support it. A sidearm slot with proper delayed trunk rotation can be highly efficient. A sidearm slot without that coordination can produce the opposite outcome, as the high school data in this study showed.
This study reinforces a principle that keeps showing up across the research: the arm is at the mercy of the torso. Arm slot is linked to shoulder abduction and lateral trunk tilt, but the timing of trunk rotation relative to arm position determines whether that slot is efficient or costly. Professional pitchers with lower slots showed reduced joint stress because their sequencing supported that position. High school pitchers with the same slots showed increased stress because their sequencing didn't. The positioning of the torso ultimately dictates where the arm ends up. As for what dictates the position of the torso, that's a much more individualistic conversation, and one that will likely always be up for debate.
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