Almost every pitcher who has tried to clean up an arm path, shorten a stride or add hip rotation has lived through the same week: the new move feels strange, the ball goes everywhere and the gun reads lower than it did before. The natural reaction is to decide the change was wrong. Motor learning research suggests a more patient reading, because individual learners rarely improve in a smooth line, and the noisiest stretch often comes just before a new pattern settles in [1, 2, 5].
That does not mean every bad week is secretly progress. Some changes really are a poor fit for your body. The goal of this article is to explain why the dip happens and then give you a practical, two-stage way to decide whether a change deserves more time.
Is it normal to get worse after a mechanical change?
Yes, and the reason starts with how learning curves are drawn. The smooth, rising curve in textbooks is mostly a product of averaging many people together. Heathcote and colleagues re-analyzed a large body of practice data and found that averaging across learners can manufacture the familiar smooth shape, even when individuals follow a different pattern [1]. Statistician W. K. Estes made the same warning decades earlier: curves built from group data can misrepresent how any single person learns [3]. Gallistel and colleagues showed the effect vividly in animal conditioning, where gradual group curves concealed abrupt, step-like individual curves [2]. That study is about animals, so treat it as a demonstration of the averaging problem rather than as pitching evidence.
Rob Gray, a perception and action researcher who writes extensively about baseball, summarizes the individual picture well: progress at the level of one athlete very rarely follows a smooth path. Long flat stretches and sudden jumps are the norm, sometimes after a slide backward [4].
Why does learning get messy right before it clicks?
The most useful study here is about a balance-type task, which sounds far from pitching but shows the mechanism clearly. Liu, Mayer-Kress and Newell tracked people learning a roller-ball task and found several distinct learning patterns. Only the participants who truly learned the task switched to a new coordination pattern, and that switch was preceded by a rise in performance variability [5]. In plain terms, the mess came first.
Coordination research adds a second layer. Kostrubiec and colleagues found that people reach a new movement pattern by one of two routes. Some slide an existing pattern over gradually, which is smoother and less variable. Others build a brand-new stable pattern, which comes with a large burst of variability but ends in greater stability [6]. Which route you take depends on the tendencies you bring in. Two pitchers given the same cue can therefore have very different first weeks, and the one who looks worse may be the one building something more durable.
These landmark studies use lab tasks such as finger rhythms and roller balls. Applying them to pitching is a reasoned extension, and no published study has mapped the learning curve of a mechanical change in pitchers.
Why are my first throws of the day worse than yesterday's last ones?
Learning runs on two clocks. Newell and colleagues separated a fast, temporary adaptation process from a slow, persistent learning process, with time scales roughly ten times apart [7]. The fast gains you make within a session tend to fade overnight, which produces a warm-up decrement at the start of the next one. The slow component can improve between sessions, during rest, by as much as or more than it does within them [7].
For a pitcher, this explains a common frustration. You finish Tuesday's bullpen feeling like the new move finally clicked, then Thursday's first ten throws look like week one again. That pattern is expected. Comparing Thursday's first throws with Tuesday's last throws is an unfair test. Compare matched points instead, such as the middle of each session after a full warm-up.
How hard is it to actually change a delivery?
Harder than most players and parents expect. Fleisig and colleagues evaluated 46 pitchers, from high school to MLB, twice, roughly a year apart. At the first evaluation each pitcher received a report explaining which of eight kinematic parameters fell outside an elite range. At the second evaluation, only 44% of those flaws had been corrected [8]. Flaws at or just after foot contact were fixed more often than flaws near ball release. The study had no comparison group, so it cannot tell us which coaching method works best, but it does show that knowing about a flaw is a long way from changing it.
Practitioners are blunt about the risk too. In a 2026 video on changing mechanics, Tread Athletics' Ben Brewster argues that a change should earn its way into the delivery, and suggests that for high-level college and pro pitchers, more often than not a change makes things worse [9]. That is a coach's opinion, but it is a useful counterweight to the idea that every flagged angle needs fixing. In our experience, youth and high school pitchers with more room to grow usually have friendlier odds. Our guide to pitching mechanics that actually matter covers which positions are worth chasing.
Compare clips across weeks
Review your delivery with Pitch AI
Pitch AI's AI Video Review breaks down your delivery with cues and top fixes, so you can compare clips from before and after a change instead of relying on how one session felt. Every throwing session you log also builds your workload progressively, which makes it easier to separate a learning dip from a tired arm.
How long should you give a mechanics change?
Use two stages, because the research on dips and the coaching advice on early warning signs are both right about different things.
Stage 1: a quick screen in the first session
Tread's approach is a fast first check. If you are badly spraying the ball after the first 10 to 20 throws, or you are slower at the same effort, step back [9]. Brewster also describes a blind split test: a partner hides the radar readings while you alternate old and new versions for five or six throws each at equal effort. A gain of one to three mph is a good sign, equal velocity is acceptable, and slower or harder-feeling throws for the same velocity is a reason to drop it [9]. This screen catches changes that cost velocity outright, which a learning dip should not excuse.
Stage 2: a longer window for command and consistency
If a change passes the screen, give it a few weeks of consistent exposure before passing judgment on command. Decide in advance what working means, for example a zone rate at or above your old baseline over a set number of bullpens. The nonlinear learning research suggests that a flat or messy first week or two is consistent with a real reorganization [5, 6, 7], so a decision made after three bad days is likely to be noise.
What to measure during the window
- Rolling averages over single days. Track velocity, zone rate, miss distance and arm feel across several sessions. One great or awful bullpen tells you very little.
- Matched comparison points. Compare sessions after a full warm-up and at similar pitch counts, because of the warm-up decrement described above [7].
- Retention and transfer. The real test is whether the pattern holds days later and shows up against hitters, which is a separate question from how it looks in the middle of one session.
- Video at regular intervals. Film from the same angles every week or so. Our guide to filming pitching mechanics covers frame rates and camera positions.
When a dip is not a learning dip
Not every drop is learning. Fatigue, poor sleep, soreness or a spike in throwing volume all produce slower, wilder throws, and they can coincide with a mechanical change. Before you credit a dip to reorganization, rule those out. If your acute workload jumped the same week you started the change, you cannot tell which one is responsible. Our article on pitching workload and arm health explains how to read acute and chronic load together. Pain is never part of a learning curve: stop and see a qualified clinician.
Timing matters as well. Brewster recommends making big changes early in the offseason and limiting in-season adjustments to small setup tweaks [9]. A big reorganization in the middle of a season stacks the dip on top of games that count.
What to do this week
- Write down one change, the reason for it and what success will look like in three to six weeks.
- Run the quick screen in your first session and drop the change if it clearly costs velocity at equal effort.
- Log every session and compare rolling averages across several sessions.
- Hold your throwing volume steady while you learn, so the workload and the mechanics are not changing at once.
A change can also ripple through the rest of your delivery in ways you did not expect, which is the subject of the next post in this series: why fixing one mechanical flaw doesn't fix your pitching. And when a new pattern holds in practice but disappears in games, read why pitchers go back to old mechanics in games.
Frequently asked questions
Is it normal for velocity to drop after changing mechanics?
A short-term drop in control is common while a new pattern forms, because variability often rises before a new coordination pattern stabilizes. A clear velocity loss at equal effort in the first session is different: Tread's coaches treat that as a reason to step back rather than wait it out.
How long does it take for a pitching mechanics change to stick?
There is no pitching-specific number. Lab research shows individual learning tends to stall and then jump, so a practical window is a few weeks of consistent exposure, judged with rolling averages and matched comparison points instead of single sessions.
Why am I worse at the start of a session than at the end of the last one?
Fast, within-session gains tend to fade overnight while slower learning consolidates between sessions. Newell and colleagues called the result a warm-up decrement. Compare sessions at matched points after a full warm-up.
Do pitchers usually fix the flaws on a biomechanics report?
Not reliably. In a study of 46 pitchers who received biomechanical reports, only 44% of flagged flaws were corrected about a year later. Knowing about a flaw is only the first step.
Judge changes on trends
Give your next mechanical change a fair test
Use Pitch AI's AI Video Review for cues and top fixes, and log every throwing session so your workload builds progressively. The daily Wellness Check-In tracks arm freshness and soreness, so you can rule out a heavy arm before you blame the new pattern. Then judge the change across weeks, the way learning actually happens.
Sources and further reading
- Heathcote A, Brown S, Mewhort DJK (2000). The power law repealed: the case for an exponential law of practice. Psychonomic Bulletin & Review 7(2):185-207. https://doi.org/10.3758/BF03212979
- Gallistel CR, Fairhurst S, Balsam P (2004). The learning curve: implications of a quantitative analysis. PNAS 101(36):13124-13131. https://doi.org/10.1073/pnas.0404965101
- Estes WK (1956). The problem of inference from curves based on group data. Psychological Bulletin 53(2):134-140. https://doi.org/10.1037/h0045156
- Gray R (2021). How We Learn to Move: A Revolution in the Way We Coach & Practice Sports Skills. Perception Action Consulting & Education. Chapter 6.
- Liu Y-T, Mayer-Kress G, Newell KM (2006). Qualitative and quantitative change in the dynamics of motor learning. Journal of Experimental Psychology: Human Perception and Performance 32(2):380-393. https://doi.org/10.1037/0096-1523.32.2.380
- Kostrubiec V, Zanone P-G, Fuchs A, Kelso JAS (2012). Beyond the blank slate: routes to learning new coordination patterns depend on the intrinsic dynamics of the learner. Frontiers in Human Neuroscience 6:222. https://doi.org/10.3389/fnhum.2012.00222
- Newell KM, Mayer-Kress G, Hong SL, Liu Y-T (2009). Adaptation and learning: characteristic time scales of performance dynamics. Human Movement Science 28(6):655-687. https://doi.org/10.1016/j.humov.2009.07.001
- Fleisig GS, Diffendaffer AZ, Ivey B, Aune KT (2018). Do baseball pitchers improve mechanics after biomechanical evaluations? Sports Biomechanics 17(3):314-321. https://doi.org/10.1080/14763141.2017.1340508
- Tread Athletics (Brewster B) (2026). Throw Harder By Changing Your Pitching Mechanics [The Right Way]. YouTube, September 24, 2026. Practitioner video. https://youtu.be/_EilR25ydwY