When the pitch clock debuted in Major League Baseball in 2023, the motivation was entertainment, not medicine. Shorten games, keep fans engaged, and modernize the pace of play.

But the assumption was immediate and nearly universal: giving pitchers less time between pitches would accelerate fatigue and increase injuries. For a generation, “fatigue equals risk” has been the cornerstone of workload management. More pitches, less rest, higher breakdown. Simple math.

Yet Card et al. (2025) provide one of the first detailed looks at the injury consequences of the pitch clock, and the findings force us to challenge that equation. UCL tears didn’t increase. In fact, pitchers tolerated significantly greater workloads before their elbows gave out.

The paradox is clear: shorter games, faster pace, and more workload tolerance. How do we explain this?

What the Study Found

Card and colleagues analyzed MLB pitchers who suffered UCL tears across two eras: pre-pitch clock (2021–2022) and post-pitch clock (2023–2024). Using public injury databases and advanced pitching workload metrics, they compared incidence rates, workloads, and demographics.

The results surprised nearly everyone:

1. UCL injury rates were unchanged — 0.63 per 1,000 innings before the pitch clock, 0.67 after.
   
   
2. Pitchers accumulated more pitches before injury — 721 vs 442.
   
   
3. They logged more innings before injury — 45.7 vs 26.5.
   
   
4. Seasonal workloads rose dramatically — 61% more pitches per season, nearly 20 more per game.
   
   
5. The profile of injuries shifted — affected pitchers were younger (28.4 vs 31.0) and more often starters than relievers.
   
   

This paints a complicated picture. The clock didn’t solve the injury problem — elbows are still failing — but it did restructure how workload and injury interact.

Fatigue, Time, and Coordination

To understand the paradox, we need to think about fatigue differently. For decades, fatigue in pitching has been framed as an inevitable linear accumulation: every additional throw brings you closer to breakdown. But this model ignores the role of time.

The pitch clock shortened average game length by about 30 minutes. Less time standing around between pitches and between innings means less cumulative exposure to the stress of competition.

That doesn’t mean pitchers are “less tired.” Instead, they may be staying in rhythm — maintaining neuromuscular coordination and mechanical efficiency across outings. This is critical, because coordination breakdowns often precede spikes in joint loading.

In simpler terms: fatigue isn’t just about the number of pitches. It’s about how effectively the body manages those pitches across the timeline of a game.

Central vs Peripheral Fatigue

Two key fatigue pathways help explain this:

• Central fatigue: the brain and spinal cord reduce motor drive, lowering the ability to coordinate movement.
  
  
• Peripheral fatigue: changes in muscle and local metabolic environment (hydrogen ion accumulation, glycogen depletion) reduce force output.
  
  

With longer rests, pitchers may actually experience more peripheral drift — cooling down, losing muscle readiness, and then re-ramping repeatedly. Similarly, central fatigue may increase when the nervous system is forced to sustain heightened arousal over prolonged, drawn-out games.

By compressing time, the pitch clock may reduce these forms of cumulative fatigue, even if pitch totals rise.

Starters vs Relievers: A New Distribution

One of the most interesting findings is the demographic shift. Before the pitch clock, relievers were more vulnerable. Now, starters represent a larger share of UCL tears.

Why? Starters face the densest exposure under the clock. Instead of spreading 100 pitches across three-plus hours, they’re condensing that workload into two and a half. Relievers, on the other hand, may benefit from more predictable rhythms and fewer prolonged idle periods in games.

The bottom line: the pitch clock didn’t reduce risk overall — it redistributed it.

Younger Pitchers at Greater Risk

The other shift is age. Injured pitchers under the clock averaged 28.4 years, compared to 31.0 before. This could suggest that younger pitchers — who throw harder and shoulder higher expectations for velocity — may be less equipped to sustain dense workloads. Their elbows may be experiencing failure earlier in careers as a byproduct of both velocity demands and game tempo.

This raises important questions about development: Are younger arms being prepared for the density of the pitch clock era? Or are we seeing the long-term effects of athletes specializing earlier, throwing harder, and accumulating stress before entering the league?

What This Means for Amateur and College Pitchers

It’s tempting to view this as an MLB-only problem, but the implications extend downward.

In college and high school baseball, pitchers often face slower-paced games. Long innings with multiple errors, extended at-bats, and inconsistent rhythms stretch outings well beyond MLB tempo. Ironically, while pros benefit from the pitch clock’s compressed rhythm, amateurs may be more exposed to the risks of prolonged fatigue accumulation.

That means that without structural changes, amateur pitchers may face greater relative stress per outing than professionals. In practice, this means:

• Bullpen sessions and scrimmages should mirror tempo, not just volume.
  
  
• Recovery should account for total time on the mound, not just pitch counts.
  
  
• Coaches should resist the urge to equate high pitch totals in slow-paced games with the same stress levels as fast-paced MLB workloads.
  
  

Rethinking Recovery

If exposure time is a hidden variable in injury risk, then recovery efficiency becomes even more critical. Protecting elbows may require new emphasis on:

• Between-inning resets: breathing, targeted mobility, and reactivation to maintain readiness.
  
  
• Postgame efficiency: quick transition into recovery modalities instead of extended ramp-downs.
  
  
• Starter-specific programming: because they now absorb the brunt of tempo-driven workload density.
  
  

At VeloU, we emphasize not just how much pitchers throw, but how they throw within the time constraints of the modern game. The clock itself is a biological stressor, and it demands a corresponding adaptation in recovery design.

Caution: More Pitches Before Injury Doesn’t Mean Safer

One misinterpretation of Card et al. would be to say the pitch clock is “protective.” But more pitches before injury doesn’t mean the tissue is healthier — it means pitchers lasted longer before catastrophic breakdown.

This distinction matters. If microtrauma accumulates silently, pitchers may cross thresholds without warning signs. The result is fewer gradual flare-ups but more complete ligament failures. In that sense, the pitch clock could be masking early warning signs rather than eliminating them.

Implications for Development Programs

So what do we take away?

1. Tempo matters as much as volume: Workload must be measured in terms of density and exposure time, not just totals.
   
   
2. Starters need tailored protocols: They are now the most vulnerable group under the clock’s tempo.
   
   
3. Younger pitchers need preparation: High-velocity, younger arms must be trained not just for strength but for efficiency under dense workloads.
   
   
4. Amateurs are different: Without a pitch clock, slower games may create the opposite problem — extended exposure that accumulates fatigue in hidden ways.
   
   

At Applied Baseball Science and VeloU, these insights push us to simulate game tempo in training, to prioritize rapid recovery strategies, and to rethink how we define “fatigue management.”

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The pitch clock was supposed to increase injuries. Instead, it revealed a deeper truth: the way time is distributed during games matters just as much as the number of pitches.

By shortening games, MLB may have inadvertently protected pitchers from certain fatigue pathways, even as it shifted the burden toward younger starters.

Protecting pitchers in this new era isn’t just about lowering pitch counts. It’s about managing rhythm, recovery, and density. The paradox of the pitch clock is that less downtime may actually mean more resilience — but only if we learn how to adapt.

Reference

Card, J., et al. (2025). The Effect of the Pitch Clock on UCL Injury Incidence and Workload in Major League Baseball Pitchers. American Journal of Sports Medicine.

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