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A shoulder that looks “healthy” on paper isn’t always the same shoulder that throws a baseball the same way. Nowhere is that clearer than in pitchers recovering from SLAP repair. For years, surgeons have pointed to the biceps anchor as a fixable lesion and a clear source of shoulder pain. But fixing anatomy doesn’t always restore movement.
A 2014 study from the American Sports Medicine Institute—led by Laughlin, Fleisig, and Dugas—examined what happens after the repair: when clearance is granted, velocity returns, and the motion still looks subtly off. Thirteen collegiate and professional pitchers with a history of SLAP repair were compared against fifty-two matched controls.
What they found is deceptively simple:
Pitchers after SLAP repair threw with ~10° less external rotation, half the horizontal abduction, and a more upright trunk at release. They had, in biomechanical terms, recovered their output but not their shape.
That mismatch between function and form raises a deeper question: how do athletes sustain pre-injury performance when the kinematic windows have narrowed—and what might that mean for long-term efficiency, spin, and health?
SLAP lesions—tears of the superior labrum where the long head of the biceps attaches—became one of the most common surgical findings in throwing athletes by the 2010s. Between 2002 and 2010, the number of SLAP repairs increased over 450 %, eventually accounting for 10 % of all shoulder surgeries in U.S. orthopedics.
For pitchers, this rise came with a mixed track record. Only about 57 % of elite throwers fully returned to their previous level of performance after SLAP repair. In theory, the procedure restores shoulder stability and pain-free motion. In practice, the tightened anterior-superior capsule can restrict the very movements that make elite velocity possible—namely external rotation and horizontal abduction during the cocking phase.
What Laughlin and colleagues wanted to know was whether those mechanical changes persisted even after rehabilitation and clearance—and whether they actually affected performance.
The study used ASMI’s 3D motion-capture laboratory to analyze pitchers who were at least one year post-operation and cleared for full-effort throwing.
The authors measured variables across the throwing chain:
Each measure was averaged across trials, with group differences assessed via Student t-tests (α = .05).
Even a modest reduction here is substantial. Ten degrees less layback reduces the stretch potential across the anterior capsule and elastic loading of the shoulder-internal-rotator musculature. In practice, that should decrease velocity. Yet these pitchers maintained their speed.
Interpretation: The repaired capsule likely constrained maximal layback, either through surgical overtensioning or residual stiffness. To maintain velocity despite this, pitchers likely compensated elsewhere—perhaps by altering timing of trunk rotation, increasing arm path efficiency, or subtly raising release height. The kinetic system delivered the same outcome through a different route.
Horizontal abduction—the amount the upper arm moves behind the body—helps load the posterior shoulder before acceleration. Cutting this range in half means the arm starts acceleration closer to the midline, reducing the visible “scap load” coaches often associate with whip.
Interpretation: This reduction probably reflects protective adaptations—either conscious (avoiding the peel-back tension that caused the original injury) or structural (tightened posterior capsule and labral anchor). It also suggests that post-repair throwers may rely more on rotational velocity timing than on arm separation for force development.
Pitchers in the SLAP group released the ball with a more upright torso—roughly 4° less forward lean.
Interpretation: Forward trunk tilt is a strong correlate of both release extension and perceived velocity. Reduced tilt may reflect either subconscious “guarding” of the shoulder or altered kinetic timing—releasing the ball slightly earlier to avoid maximal shoulder stretch. Coaches often describe this as a pitcher who looks like he’s “pushing the ball.”
No significant differences appeared in internal-rotation torque or elbow-flexion torque, angle, or velocity.
Interpretation: Despite altered shoulder kinematics, joint loading at the elbow remained similar. That’s a double-edged sword: the body achieved equivalent torque production without the same mechanical windows. This suggests compensation elsewhere in the chain—possibly through earlier trunk rotation or higher muscular effort from the torso and scapular stabilizers.
Lower-body mechanics did not differ. The compensation was isolated to the upper half, supporting the idea that pitchers maintained their delivery pattern but compressed the upper-body motion within it.
The most striking part of this study is what didn’t change: velocity. If pitchers throw just as hard with less external rotation and less horizontal abduction, it means they’ve learned to re-organize the kinetic chain around new structural limits.
That’s a triumph in the short term—but it raises long-term concerns. Reduced layback shrinks the elastic contribution from the shoulder capsule, forcing the torso and arm musculature to carry a larger share of acceleration work. Over time, that can mean higher relative muscle effort for the same output and potential downstream effects on recovery, fatigue resistance, and pitch shape.
From a mechanical standpoint, it’s a version of the “same output, narrower funnel” problem: you can pour the same volume through a smaller opening, but the pressure inside the system increases.
If velocity is maintained but motion is constrained, where does the energy come from?
Three plausible sources emerge:
These are adaptive, not necessarily pathological, changes—but they highlight how complex “return to play” really is. Clearance doesn’t mean the system is identical. It means the system has reorganized itself to survive.
This research measured joint kinematics and kinetics, but not ball flight metrics. We don’t know whether reduced shoulder motion affected spin rate, axis, or movement consistency.
Intuitively, a narrower arm path could:
So while velocity held, pitch quality might not have. That’s a critical distinction for coaches managing post-SLAP athletes: radar readings tell one story, ball metrics tell another.
Laughlin et al. concluded that external-rotation and horizontal-abduction range should be primary restoration goals post-surgery. The problem is structural: surgical overtensioning and conservative early rehab can permanently reduce these motions.
At the tissue level, even a few degrees of excessive tightness in the anterior capsule increases resistance during cocking. Once scarred, that stiffness is difficult to reverse. Physical therapy must therefore balance protection of the repair with early controlled restoration of external rotation and abduction—especially in the 90° abducted position relevant to throwing.
In simple terms: fixing stability can’t come at the cost of function.
A pitcher one year post-SLAP repair may be pain-free and “game-ready,” but his kinematic profile could still differ substantially from baseline. Re-testing motion—particularly layback, scap load, and trunk posture—is critical.
Since forward trunk tilt decreased, incorporate drills emphasizing late trunk flexion and controlled forward rotation. Example: tempo holds at foot-plant with delayed trunk drive or “towel whip” patterns reinforcing forward tilt through release.
Passive and active external rotation at 90° abduction should be an explicit rehab target once the repair is stable. Avoid chronic overtightening of the anterior capsule.
If the athlete is throwing as hard with less motion, evaluate recovery metrics and command variability. Efficiency costs can hide behind stable radar numbers.
Coaching “shorter arm action” or “stay compact” in an already ROM-limited athlete could amplify the restriction and push stress toward the elbow.
At VeloU, we’ve seen this pattern firsthand: post-SLAP athletes often show unchanged output but altered delivery shape. Our approach is to measure not just speed, but how that speed is produced.
This is the modern definition of “return to play”: not merely throwing hard again, but throwing efficiently again.
Laughlin’s 2014 study remains one of the few that quantified post-SLAP pitching mechanics. Its message is subtle but profound: the shoulder can be “healed” yet still move differently. When layback and separation shrink, the pitcher doesn’t necessarily slow down—he reorganizes.
For the surgeon, this underscores the importance of anatomic, non-tensioned repairs.
For the therapist, it highlights the need to re-earn end-range external rotation early and progressively.
For the coach, it’s a reminder that clearance doesn’t mean completion.
A pitcher can look fine, throw hard, and still be working inside a smaller biomechanical box. The art is recognizing that—and rebuilding trust, motion, and efficiency before that box becomes a cage.
Laughlin, W. A., Fleisig, G. S., Scillia, A. J., Aune, K. T., Cain, E. L., & Dugas, J. R. (2014). Deficiencies in pitching biomechanics in baseball players with a history of superior labrum anterior-posterior repair. The American Journal of Sports Medicine, 42(12), 2837–2841. https://doi.org/10.1177/0363546514552183
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