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There's a question that doesn't get asked nearly enough in baseball: why are we lifting the day after a pitcher starts? It's become standard practice at nearly every level, a box checked on the weekly schedule without much thought given to whether it actually makes sense. The logic usually goes something like this: the pitcher threw yesterday, so today is a "recovery day," and recovery days include light lifting to get blood flowing and promote tissue repair. It sounds reasonable on the surface. But what if the underlying assumption is wrong? What if the body isn't ready to absorb even moderate training stress 24 hours after a start?
A 2017 study by Cornell and colleagues tracked resting heart rate variability across a 5-day rotation in professional starting pitchers, and the findings should give every coach and athlete pause. Using lnRMSSD, a widely accepted marker of autonomic nervous system activity, the researchers found that HRV was significantly suppressed on Day 2 post-start, indicating that the body was still locked in a sympathetic, stress-dominant state a full 24 hours after taking the mound. It wasn't until Day 3 that HRV returned to baseline in most pitchers, implying that full autonomic recovery takes approximately 48 hours. At Velo University, we've long avoided next-day lifts for this exact reason. This study finally puts data behind what many of us have suspected: forcing intensity during this window may not just delay recovery, it could prolong stress, raise injury risk, or mute adaptation entirely.
The researchers tracked professional starting pitchers across their 5-day rotation, measuring resting HRV each morning using lnRMSSD. For those unfamiliar, lnRMSSD is the natural log of the root mean square of successive differences in heartbeat intervals. In simpler terms, it measures the variation in time between heartbeats, which reflects the balance between your sympathetic (fight or flight) and parasympathetic (rest and digest) nervous systems. Higher HRV generally indicates a body that's recovered, adaptable, and ready to handle stress. Lower HRV suggests the system is still taxed, still working to restore balance.
What the researchers found was a clear and consistent pattern. On Day 2, the day after a start, HRV was significantly suppressed compared to baseline. This suppression indicates elevated sympathetic tone and reduced parasympathetic recovery, meaning the body hadn't yet shifted out of its stress response. The pitcher may have felt fine. He may have slept eight hours and eaten well. But his autonomic nervous system was telling a different story, one that subjective feel alone couldn't capture. By Day 3, HRV returned to baseline in most pitchers, suggesting that approximately 48 hours is required for full autonomic recovery following a start.
One of the more compelling aspects of this study was the lack of a pitcher-by-day interaction effect. In other words, the Day 2 dip wasn't just happening in some pitchers, it was consistent across the group. This wasn't a case of a few outliers dragging down the average. The pattern was reliable and reproducible, which makes it much harder to dismiss as noise or individual variation.
However, and this is where it gets interesting, baseline HRV varied greatly between athletes. Some pitchers walked around with naturally higher parasympathetic tone, while others ran closer to the sympathetic end of the spectrum even at rest. This individual variability reinforces a critical point: recovery timelines are personal, not universal. Two pitchers on the same staff, throwing the same number of pitches, may require very different recovery windows. One may bounce back by Day 2. Another may still be suppressed into Day 3 or beyond. Without tracking, you'd never know the difference. You'd just be guessing, and guessing with pitcher health tends to have consequences.
To be honest, this study challenges a lot of what has become conventional wisdom in baseball. The idea that a pitcher should lift the day after a start has been baked into programming for years, often justified by the belief that "active recovery" or "getting blood flow" accelerates the process. But if HRV, a direct window into your body's recovery state, is still depressed 24 hours after you pitch, what exactly are we recovering from by adding more stress?
This isn't just about feeling tired. The autonomic nervous system governs far more than perceived fatigue. It regulates inflammation, tissue repair, hormonal balance, and the body's ability to adapt to training. When you're locked in a sympathetic state, your system is prioritizing survival, not growth. Layering a lifting session on top of that doesn't accelerate recovery. It competes with it. And competition for recovery resources is a zero-sum game. Every stressor you add during a suppressed window is a stressor the body has to manage before it can get back to baseline.
Research on adolescent pitchers has shown that fatigue effects emerge after as few as 35 pitches, with pelvic rotation velocity dropping and hip-to-shoulder separation decreasing as the outing progresses. If fatigue is already altering mechanics during the game itself, the residual effects the next day are likely more significant than we appreciate. The lower body drives the pitching motion, and when it fatigues, the arm compensates. That compensation doesn't just disappear overnight.
A 2025 study found that pitch count, RPE, and even arm-specific RPE were not significantly associated with musculoskeletal changes in adolescent pitchers. External rotation strength dropped immediately post-game but returned to baseline within 24 hours and actually exceeded baseline by Day 5. This tells us two things: first, that pitch count alone is an incomplete measure of stress, and second, that the body does recover, but on its own timeline. The fact that strength exceeded baseline by Day 5 suggests a supercompensation effect, but only if the body is given the time and resources to get there.
The research on perceived effort is equally humbling. A 2023 motion capture study found that when pitchers were asked to throw at 75% effort, their elbow stress was still 81% of max. At 50% effort, stress only dropped to 74%. For every 25% decrease in perceived effort, elbow stress dropped just 13%. Subjective feel is not a reliable proxy for objective load. If we can't trust perceived effort during throwing, why would we trust perceived readiness the day after? Athletes are notoriously bad at sensing their own recovery status, partly because the sympathetic nervous system that's keeping them suppressed is also making them feel alert and ready to go. The stress response doesn't feel like exhaustion. It feels like activation.
Sleep research adds another layer to this conversation. A study on competitive Canadian athletes found that 84% of those with sleep disturbances reported a direct link between poor sleep and recurring injuries or slower recovery. And the mechanism is clearer than ever. A 2025 study published in Cell mapped how growth hormone, the driver of tissue repair and adaptation, is released in short bursts during early deep sleep and again during REM. Push bedtime later, fragment your sleep, or add stress that disrupts sleep quality, and you risk blunting the very hormonal signals that make recovery possible.
Even the research on elbow tissue recovery reveals nuance. A 2025 study found that medial elbow joint space returned to baseline within 24 hours after 100 pitches, which sounds reassuring. But forearm flexor-pronator muscle strain actually increased after 24 hours, suggesting that systemic fatigue lingers even when local tissue appears recovered. The elbow might feel fine, but the muscles responsible for stabilizing it are still catching up.
There's also a mechanistic angle worth considering. A 2022 study on nicotine's acute effects in baseball players found that even a small dose drove sympathetic nervous system dominance, with reduced HRV and elevated stress markers. The athletes showed improved reaction time and motor precision, but at the cost of parasympathetic recovery capacity. This illustrates how easily the autonomic balance can be shifted, and how substances or stressors that feel performance-enhancing in the moment can compromise recovery on the back end. The same logic applies to training. A lift that feels productive on Day 2 might be stealing resources from the recovery process that's still underway.
The practical application here is straightforward, even if it requires a shift in thinking. Daily HRV tracking is low-lift to implement and high-impact when used correctly. A simple morning measurement, taken before getting out of bed, can tell you more about an athlete's readiness than any pitch count or subjective questionnaire. The key is establishing individual baselines and tracking trends over time, not chasing a single number. One pitcher's baseline might be 65. Another's might be 85. What matters is where they are relative to their own normal, and whether they're trending up, down, or holding steady.
If HRV is still suppressed on Day 2, that's a signal. It doesn't mean the athlete can't do anything, but it does mean that high-intensity lifting or additional throwing stress is probably not the best use of that window. Low-intensity movement, mobility work, or mental skills training might be more appropriate. The goal is to support recovery, not compete with it. This isn't about being soft or avoiding work. It's about being strategic with when and how stress is applied.
Research on resistance training fatigue supports this approach. A systematic review found that higher velocity loss during lifting led to greater fatigue markers, including elevated blood lactate and RPE, while power output declined. Low-to-moderate velocity loss, in the 10-25% range, achieved the optimal balance between stimulating adaptation and preserving neuromuscular speed. For baseball athletes, this reinforces that training fatigue must be managed, not maximized. Power-based adaptations depend on high-quality, high-velocity reps. If your system is already suppressed, the quality of those reps suffers, and so does the adaptation. You end up doing work that looks productive on paper but doesn't actually move the needle.
What makes HRV even more powerful is its individual specificity. A 2019 study on long-toss variability found that torque varied widely between pitchers, even when throwing at the same distances and intensities. Stress is highly individual. The same workload that one pitcher absorbs easily might push another into a prolonged recovery window. Without individualized monitoring, you're guessing. And guessing with pitchers tends to go poorly over time.
There's also emerging evidence that HRV can be used as an intervention tool, not just a monitoring metric. A 2025 study on college baseball players found that just 10 days of HRV biofeedback training reduced cognitive anxiety and significantly improved batting performance. The experimental group saw batting scores double, along with improvements in contact quality and infield hit ratio. If HRV-based training can shift psychological readiness that quickly, imagine what respecting HRV-based recovery windows could do for physical readiness over a full season. The autonomic nervous system isn't just a reflection of recovery status. It's a lever that can be trained and optimized.
For coaches and organizations, the implementation doesn't have to be complicated. There are affordable apps and chest straps that can capture morning HRV in under two minutes. The data can be logged and reviewed weekly, with programming adjusted based on individual trends. Athletes who consistently show suppressed HRV on Day 2 might benefit from a modified schedule that pushes their primary lift to Day 3. Athletes who bounce back quickly might be able to handle more. The point isn't to create a rigid protocol. It's to create a feedback loop that allows programming to adapt to the athlete.
The data here is clear. HRV remains suppressed for approximately 48 hours after a start, and that suppression is consistent across pitchers even though baseline values vary widely between individuals. Forcing intensity during this window, whether through lifting or additional throwing, doesn't accelerate recovery. It competes with it. At Velo University, we've structured our programming around this principle for years, and the research continues to validate that approach. The best part is that HRV tracking is simple, inexpensive, and actionable. You don't need a lab. You need a consistent morning routine and a willingness to let the data guide your decisions. Recovery isn't about checking boxes on a schedule. It's about understanding when your body is actually ready to absorb stress, and when it needs more time.
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