Summary
Dean Jackson is a former professional pitcher who now trains athletes across MLB, AAA, Liga Mexicana, and other professional baseball environments. In the first article in this miniseries, Dean used Incremental Velocity Analysis to examine how pitchers create additional velocity. In the second, he compared pulldowns with mound throws to see whether added forward momentum changed how the throwing arm moved.
For the final installment, Dean turns to a different question: what changes across a single 50-pitch bullpen as the throwing arm becomes fatigued?
Measuring the Shoulder Before and After the Bullpen
The pitcher completed 50 pitches over three innings. Before the bullpen, Dean and his collaborators used a Biodex system to perform a supermaximal eccentric assessment of the posterior rotator cuff. They repeated the same assessment after the bullpen to compare the athlete’s performance on the test before and after throwing.
That before-and-after comparison adds information that pitch count and radar cannot provide on their own. Pitch count records how much the athlete threw, and radar records the outcome of each pitch. The Biodex assessment gives Dean a separate measure of how the tested shoulder muscles responded over the course of the session.
Capturing Mechanics from the First Inning to the Last
At the same time, Dean used Theia3D to capture the pitcher’s full-body movement during the first and last innings. This creates an early-session and late-session view of the same athlete under the same bullpen protocol.
Instead of relying on a late-session velocity reading or a visual impression that the pitcher looks tired, the motion-capture data lets Dean compare how the athlete actually moved at the beginning and end of the outing.
“The Biodex assessment tells us whether the posterior rotator cuff performed differently after the bullpen. Theia3D tells us whether the athlete’s pitching mechanics changed from the first inning to the last. Combining the two gives us a much clearer picture of how the athlete responded to the session.”
Connecting What Fatigued with What Changed
Each dataset answers a different part of the question. The Biodex comparison can show whether performance in the posterior rotator cuff assessment changed from before to after the bullpen. Theia3D can show whether the pitcher’s movement pattern changed from the first inning to the last.
Used together, the two datasets allow Dean to investigate whether changes in the shoulder test occurred alongside changes in pitching mechanics. The goal is not to assume that every late-session mechanical change was caused by the rotator cuff. It is to replace a broad label like fatigue with two measurable comparisons: what changed in the physical assessment, and what changed in the throw.
“This is where Theia3D adds value: it lets us quantify how the athlete moved early and late in the bullpen instead of relying on radar or visual observation alone.”
The Takeaway: Measure More Than Pitch Count
A 50-pitch bullpen can produce the same pitch count for every athlete, but it does not follow that every athlete responds in the same way. Radar can show whether velocity changed. Standard video may reveal visible differences. Pairing strength testing with markerless motion capture adds a way to compare the athlete’s physical response with full-body movement data across the session.
For Dean, that means moving beyond the question of whether a pitcher became fatigued and toward a more useful one: Did this pitcher’s rotator cuff performance and throwing mechanics change from the beginning of the bullpen to the end?
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Interested in comparing how pitching mechanics change across a bullpen or alongside strength testing? Contact our team to learn how Theia3D can fit into your baseball performance workflow.