All studies

Does the early winner become the champion?

51 studies, 6,096 athletes, 772 world-class. Everything that predicts winning at twelve predicts not reaching the top.

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The Spark · 01Survey + review5 min

Why do children quit?

What children say when they leave — “I’m not good enough,” 29% — and what forty-three studies say is underneath it.

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The Body · 03Federation + consensus5 min

Why do girls’ times stall at thirteen?

The two halves of a question most clubs answer with “try harder.”

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The Body · 01Position statement4 min

Will strength training stunt their growth?

The question parents ask most about training — and the answer a professional body gave, in writing, in 2009.

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The Body · 02Longitudinal study4 min

Why do injuries cluster around the growth spurt?

Twenty-six talented footballers, followed for three years through the one window when a body is most changeable.

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The Energy · 01Cohort study4 min

How much does sleep actually matter?

A single school, 112 athletes, 21 months — and the plainest injury predictor anyone has found.

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The Journey · 02Meta-analysis4 min

Why does the child who won at ten get caught at fourteen?

Thirty-eight studies on a quiet advantage that decides who gets picked — and expires.

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The Body · 04Meta-analysis4 min

What can a movement screen tell you — and what can’t it?

The most-used screening tool in youth sport, and the meta-analysis that told everyone what it isn’t.

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Explore more

How we read the data

Physiology and meaning on one timeline, and why direction takes two seasons to see.

The baseline loop

What we're built on

Stanford Medicine, Dr. Stacy Sims, LTAD, GCDF — the science stack behind the method.

Our training

The Method

Four rings, one loop, and what we refuse to do.

Read the method

The Map

One page. Which stage your child is in, what it's for, and what to leave alone.

The map that has been in the science for decades and almost never reaches a family. Sent once, no follow-ups.

We use your email only for this. Privacy.

Science

The Journey · 01Meta-analysis5 min

Does the early winner become the champion?

One study, one page. The largest analysis yet of how world-class athletes actually got there — and why it says the opposite of what most clubs assume.

The question every parent asks without saying it.

If she isn't winning now, is she already behind?

Most youth sport runs on an unspoken answer: yes. Start early, pick one sport, train more than the others, win the age group — and the champion is the child who does all of that first. It is a reasonable assumption. It is also, according to the largest study ever done on the question, backwards.

The study.

In 2022, three researchers — Arne Güllich, Brooke Macnamara and David Hambrick — pooled every study they could find that had tracked how elite athletes trained as children. The result was a meta-analysis of 51 studies, 477 separate effects, and 6,096 athletes, including 772 of the world's top performers — Olympic and world-championship level, across sports and across fifteen countries.¹

They asked a simple question: what did the people who reached the very top do differently, as children, from the people who reached national level and stopped there?

They also asked it a second way: what did the best youth athletes do differently from the rest?

The two answers were opposites.

What it found.

1. World-class adults started later, trained less in their main sport, and played more of everything else. Compared with national-class athletes, the world's best "engaged in more childhood/adolescent multisport practice, started their main sport later, accumulated less main-sport practice, and initially progressed more slowly."¹

2. The best youth athletes did exactly the reverse. The children winning at twelve had "started playing their main sport earlier, engaged in more main-sport practice but less other-sports practice, and had faster initial progress."¹ Everything that predicts winning young predicts not reaching the top.

3. Unstructured play didn't move the needle either way. Pickup games and free play — "youth-led play in any sport" — had "negligible effects on both youth and adult performance."¹ The benefit came from coached practice in several sports, not from simply letting children run around.

The authors' conclusion: multidisciplinary practice is "associated with gradual initial discipline-specific progress but greater sustainability of long-term development of excellence."¹ Or, as the summary published by their own professional society put it: senior world-class athletes who began their main sport early and specialized "are the exception, not the rule."²

What it doesn't say.

It is an association, not a law. These athletes weren't randomly assigned to childhoods. The pattern is strong and consistent across 51 studies — but it describes populations, not any one child.

It does not say "don't take sport seriously." The world-class group trained hard. They trained hard in more than one thing, and they reached the top later.

It does not say "just let them play." Finding three matters: the multisport practice that helped was coach-led. Variety with structure, not variety instead of it.

At nine, thirteen, sixteen.

Nine. The child in two or three sports, not yet winning any of them, is on the world-class path. The child already specialized and dominating is on the youth-elite path — which is a different road, and a shorter one.

Thirteen. This is the age the study's two curves cross. The early specializer is peaking; the multisport child is only now pulling ahead in one thing. To everyone watching, it looks like the first child is "better." The data say: not for long.

Sixteen. Specialization now is what the world-class group did. It is the timing, not the decision, that separates the two roads.

How we use it

This is the Journey ring's first rule — sample first, specialize later — with its evidence attached. It is also why a Growth Passport at nine records which sports a child plays, not just how fast they are.

Next in this ring The Method

Sources

Güllich, A., Macnamara, B. N., & Hambrick, D. Z. (2022). What makes a champion? Early multidisciplinary practice, not early specialization, predicts world-class performance. Perspectives on Psychological Science, 17(1), 6–29. doi.org/10.1177/1745691620974772
Association for Psychological Science, Observer: "What Makes a Champion? Varied Practice, Not Single-Sport Drilling." psychologicalscience.org

All studies Why does the child who won at ten get caught at fourteen?

Science

The Journey · 02Meta-analysis4 min

Why does the child who won at ten get caught at fourteen?

One study, one page. Thirty-eight studies on a quiet advantage that decides who gets picked — and expires.

The child everyone remembers.

Every club has one. Dominant at ten, picked for every squad, first name on every list. Then at fourteen the field catches up, and the family calls it a slump.

It usually isn't. It is arithmetic.

The study.

In 2009, four researchers pooled every study they could find on a pattern that had been noticed in sport for decades: children born early in the selection year are more likely to be picked, kept, and promoted than children born late in it. Their meta-analysis covered 38 studies, 253 independent samples, 14 sports and 16 countries.¹

The pattern has a name — the relative age effect — and a simple cause. In a January-to-December age group, a child born in January has had almost a year more to grow than a child born in December. At ten, a year is a lot.

What it found.

1. The effect is everywhere. Across 253 samples the researchers found "consistent prevalence" of relative age effects — older-in-the-year children over-represented, younger-in-the-year children under-represented.¹

2. It is strongest exactly when selection happens. The context "most at risk" was "adolescent (aged 15–18 years) males, at the representative (i.e. regional and national) level in highly popular sports."¹ The bias is largest at the moment squads are chosen.

3. It is small per child — and it compounds. The authors are careful: the effect sizes are "small."¹ No single selection is decided by a birthday. But a small advantage applied at every selection, every year, from eight to eighteen, is not small by the end.

And birth month is the mild version. The same mechanism runs on biological maturity, where the gap is not months but years. Swimming Canada's own development strategy puts it plainly: "Children of the same chronological age can differ by several years in their level of biological maturation" — and "Currently, most swimming training and competition programs are based on chronological age."²

What it doesn't say.

It doesn't say late-born children can't make it. Small effect sizes mean most of them do. The point is that the system leans, not that it decides.

It measures birthdays, not bodies. Relative age is the easiest version of the problem to count. Maturity — the early grower versus the late one — is the bigger version, and harder to see without measuring it.

It doesn't blame anyone. No coach picks a child for being born in January. They pick the child who is bigger and faster today. That is the whole problem: today is not the question.

At nine, thirteen, sixteen.

Nine. A year of birth-month advantage, or a year of early growth, looks like talent. Sometimes it is. Often it is a calendar.

Thirteen. The early grower has finished growing; the others are starting. The gap closes, then reverses. This is the "slump" — and it was always going to happen on this schedule.

Sixteen. Growth is mostly done for everyone. Now the comparisons finally mean what people thought they meant at ten.

How we use it

We do not read a child's results against their age group. We read them against their growth: every screen starts with a maturity snapshot, and every plateau is dated to where the body is, not where the birthday is.

Previous in this ring The growth spurt

Sources

Cobley, S., Baker, J., Wattie, N., & McKenna, J. (2009). Annual age-grouping and athlete development: A meta-analytical review of relative age effects in sport. Sports Medicine, 39(3), 235–256. doi.org/10.2165/00007256-200939030-00005
Swimming Canada, Long Term Athlete Development Strategy (Ottawa, 2008), pp. 14–15, "Developmental Age."

All studies Will strength training stunt their growth?

Science

The Body · 01Position statement4 min

Will strength training stunt their growth?

One statement, one page. The question parents ask most about training — and the answer a professional body gave, in writing, in 2009.

The fear.

Somewhere along the way, a rumor became a rule: lifting anything heavy before puberty damages the growth plates and makes a child shorter. Most parents have heard it. Many coaches still repeat it.

The people whose job is to know looked at every study they could find, and put their answer in a position statement.

The statement.

In 2009 the National Strength and Conditioning Association — the professional body for strength coaches — published an updated position paper on youth resistance training, written by seven researchers and physicians and reviewing the accumulated research to date.¹ A position statement is not one experiment; it is a profession's considered reading of all of them.

What it found.

1. The growth-plate injury has never turned up in the research. In the statement's words: "To date, injury to the growth cartilage has not been reported in any prospective youth resistance training research study."¹

2. Done properly, it is safer than most sports. "A properly designed and supervised resistance training program is relatively safe for youth." In comparative injury data, "resistance training and weightlifting were markedly safer than many other sports and activities."¹

3. Children get measurably stronger, without bulking. Strength gains of "roughly 30%" were "typically observed after short-term (8–20 weeks) youth resistance training programs."¹ Before puberty, that strength comes from the nervous system learning to coordinate muscle — not from muscle size.

4. The starting line is readiness, not age. "If a child is ready for participation in sport activities (generally age 7 or 8 years), then he or she is ready for some type of resistance training."¹ Mayo Clinic's guidance for parents says the same: from around seven or eight, "as long as the child is mature enough to follow directions and able to practice proper technique and form."²

What it doesn't say.

It doesn't say "let them lift heavy." Every safety finding is conditional on supervision by "qualified adults who have an understanding of youth resistance training guidelines."¹ The injuries that do happen in youth weight rooms come from unsupervised lifting and poor technique — not from strength training itself.

It doesn't say bodybuilding. Mayo draws the line clearly: strength training is not weightlifting, bodybuilding or powerlifting, and "bulking up" is "most safely done after adolescence, when your child's bones have finished growing."² For children: light loads, controlled movement, "one or two sets of 12 to 15 repetitions."²

It doesn't say strength replaces sport. It says strength protects sport — stronger tissue tolerates the load a growing body is about to be asked to carry.

At nine, thirteen, sixteen.

Nine. Bodyweight, bands, technique. The goal is to learn a squat, a hinge, a push — not to load them. This is the cheapest injury insurance a child will ever buy.

Thirteen. The growth spurt. Strength work now is about keeping coordination while the limbs change length — and it is the one thing that should not be dropped when training gets busy.

Sixteen. Growth mostly done; loading can now progress toward adult patterns. The child who learned to move at nine starts here with seven years of technique in the bank.

How we use it

Strength is part of the shelter. We screen how a child moves before anyone loads them, and the corrective work that follows a screen is, in most cases, strength training by another name.

The movement screen The growth spurt

Sources

Faigenbaum, A. D., Kraemer, W. J., Blimkie, C. J. R., Jeffreys, I., Micheli, L. J., Nitka, M., & Rowland, T. W. (2009). Youth resistance training: Updated position statement paper from the National Strength and Conditioning Association. Journal of Strength and Conditioning Research, 23(5 Suppl), S60–S79.
Mayo Clinic Staff, "Strength training: OK for kids?" mayoclinic.org, Tween and teen health.

All studies Why do injuries cluster around the growth spurt?

Science

The Body · 02Longitudinal study4 min

Why do injuries cluster around the growth spurt?

One study, one page. Twenty-six talented footballers, followed for three years through the one window when a body is most changeable — and most breakable.

The year everything moves.

Between roughly eleven and fifteen, a child grows faster than at any time since infancy. Bones lengthen first. Muscles, tendons and the nervous system catch up later. For a year or so, the child is running on a body whose proportions changed faster than its control did.

Coaches know this window. Most training plans ignore it.

The study.

A Dutch research group followed 26 talented youth soccer players — average age just under twelve at the start — for three years, measuring their height regularly enough to pin down each boy's individual growth spurt (peak height velocity, or PHV), and recording every injury.¹

Because they had each child's growth curve, they could do something age-group tables can't: line up injuries against where the body was, not how old the child was.

What it found.

1. Acute injuries almost doubled in the growth-spurt year. Traumatic injuries rose from 0.81 per player in the year before PHV to 1.41 in the PHV year.¹

2. Training time lost more than doubled. Days missed rose from 7.27 per year before the spurt to 15.69 during it.¹

3. The type of injury changes after the spurt. The authors' summary: "Adolescent growth spurt seems to result in increased vulnerability for traumatic injuries. Afterwards athletes seem to be susceptible to overuse injuries."¹ First the body breaks suddenly; then, once grown, it starts to wear.

A larger study of talented youth footballers published in 2018 examined the same question — injury risk and burden in relation to age group and peak height velocity — and found the pattern held.² The growth spurt is a risk window, and it is an individual one.

What it doesn't say.

Twenty-six is a small group. The numbers are precise for these boys; they are a pattern, not a prediction, for any other child. That is exactly why the 2018 study matters — it asked the same question of many more.

It doesn't say "stop training." It says the load a body can take changes with the body. The same session that was fine at eleven can be too much at twelve-and-a-half, and fine again at fourteen.

It doesn't say when your child's window is. No calendar can. Girls typically enter the spurt around 11–13, boys around 13–15 — but "typically" hides two years of spread. Only measurement tells you.

At nine, thirteen, sixteen.

Nine. Too early for most — which makes it the right time to start measuring height every three months. The growth curve you draw now is what tells you, later, that the window has opened.

Thirteen. The window, for many. Acute injuries, sudden clumsiness, a drop in movement quality. None of it is carelessness. It is a body being rebuilt, and the training load needs to come down with it — briefly, on purpose.

Sixteen. Past the spurt for most. Now the concern flips to overuse: the wear that accumulates when a full-size body trains full-size volumes on a technique learned at eleven.

How we use it

Every screen we do starts with a growth snapshot: height, sitting height, growth rate over the last six and twelve months. A movement score that drops during the spurt is read as a load signal, not a failure — and re-screened in six to eight weeks, not twelve.

Girls at thirteen The movement screen

Sources

van der Sluis, A., Elferink-Gemser, M. T., Coelho-e-Silva, M. J., Nijboer, J. A., Brink, M. S., & Visscher, C. (2014). Sport injuries aligned to peak height velocity in talented pubertal soccer players. International Journal of Sports Medicine, 35(4), 351–355. doi.org/10.1055/s-0033-1349874
Bult, H. J., Barendrecht, M., & Tak, I. J. R. (2018). Injury risk and injury burden are related to age group and peak height velocity among talented male youth soccer players. Orthopaedic Journal of Sports Medicine, 6(12). doi.org/10.1177/2325967118811042

All studies Why do girls' times stall at thirteen?

Science

The Body · 03Federation + consensus5 min

Why do girls' times stall at thirteen?

One federation document and one medical consensus, one page. The two halves of a question most clubs answer with "try harder."

The pattern.

A girl who improved every season from eight to twelve stops improving at thirteen. Sometimes she gets slower. The coach, reasonably, looks for a training problem. The family, reasonably, looks for an attitude problem.

Two documents — one from a national swimming federation, one from the International Olympic Committee — say to look somewhere else first.

Document one: the swimming federation.

Swimming Canada's long-term development strategy has a section most parents never see, on how puberty treats the two sexes differently.² For boys, it says, the hormonal changes of puberty are "seemingly advantageous." For girls, it is direct:

"Unlike boys, development during puberty for girls can initially have a negative effect on swim performance."²

And then a sentence that should be printed on every pool-deck wall:

"It is not necessarily a change in her diet, changes in her training, or lack of willpower, but is part of her development as a female that, to a large degree, is out of her control."²

The same document notes that girls typically enter their growth spurt around 11–13, roughly two years ahead of boys — so the stall lands earlier, and lands alone.²

Document two: the medical consensus.

In 2023 the International Olympic Committee published its updated consensus on Relative Energy Deficiency in Sport — REDs — the condition that develops when an athlete's body doesn't get enough fuel to cover both training and the cost of being alive and growing.¹

The consensus describes low energy availability as existing "on a spectrum from being an adaptation that occurs naturally at high levels of exercise to being problematic for health."¹ Among the outcomes it tracks: reduced bone mineral density, loss of muscle strength, sleep disturbance, mental-health effects — and, added in this edition, growth impairment.¹

Put the two documents together and the thirteen-year-old's stall has two candidate causes, neither of which is effort: a body that is being rebuilt on a schedule of its own, and a body that may be under-fueled for the size of the job.

What it doesn't say.

It doesn't say every stall is physiology. It says physiology should be ruled out first — before anyone concludes she isn't trying.

It doesn't say girls should train less. The federation's recommendation is the opposite: training through puberty should "focus on maintaining their muscular stature."² The point is to plan for the change, not to retreat from it.

It doesn't say anything about weight. Neither document does, and neither do we. Under-fueling is measured by what goes in against what the body needs — never by what a scale says.

At nine, thirteen, sixteen.

Nine. Nothing to fix. Everything to record: height every three months, so that when the curve turns, someone notices.

Thirteen. The window. Times stall, coordination wobbles, tiredness arrives out of proportion to the training. This is the season to check fuel and sleep against load, and to say out loud — to the girl — that this was expected.

Sixteen. Growth is done, the body has settled, and the girl who was kept whole through thirteen is now training a finished body with an intact reason to be there. Many of her peers are not — they left at fourteen.

How we use it

For girls the Body ring carries an extra layer: growth tracked against the cycle, strength maintained through the spurt, and energy availability checked before any plateau is called a problem. It is the biology most programs still ignore. We don't.

The Energy ring Why children quit

Sources

Mountjoy, M., Ackerman, K. E., Bailey, D. M., Burke, L. M., Constantini, N., Hackney, A. C., et al. (2023). 2023 International Olympic Committee's (IOC) consensus statement on Relative Energy Deficiency in Sport (REDs). British Journal of Sports Medicine, 57(17), 1073–1097.
Swimming Canada, Long Term Athlete Development Strategy (Ottawa, 2008), p. 16, "LTAD Gender Considerations."

All studies What can a movement screen tell you?

Science

The Body · 04Meta-analysis4 min

What can a movement screen tell you — and what can't it?

One study, one page. The most-used screening tool in youth sport, and the meta-analysis that told everyone what it isn't.

The tool.

A movement screen is a short, standardized set of movements — a deep squat, a step over a hurdle, a lunge, a reach — scored on how well a body performs them and whether the two sides match. The best-known version, the Functional Movement Screen, takes about fifteen minutes and needs almost no equipment.

It is the first thing we do with every child. So it matters that we are clear about what it does and doesn't do.

The study.

For years the screen was sold on a promise: a low score predicts injury. In 2017 four researchers pooled every study that had tested that promise and published a systematic review with meta-analysis in the British Journal of Sports Medicine.¹

What it found.

Their conclusion was unambiguous: the strength of association between a screen's total score and later injury "does not support its use as an injury prediction tool."¹

That is a sentence we quote on purpose. The screen is not a crystal ball. A child with a low score is not destined to be hurt, and a child with a high score is not safe.

What it can do.

The same body of research leaves three uses standing — and they are the three we use it for:

1. It describes how a child moves, today, in a way that can be compared with tomorrow. The same seven patterns, the same order, the same scoring, repeated every quarter. A screen is a ruler, not a forecast — and rulers are what you need to see change.

2. It finds asymmetry. A left side that scores differently from the right is the single most useful thing a screen turns up, and it is invisible in normal training. Our own protocol treats an asymmetry as a higher priority than a low total.²

3. It turns "she moves a bit awkwardly" into three specific decisions. Which pattern to correct first, what to hold off loading until it improves, and when to re-check. That is the entire purpose: a screen is only worth doing if it changes what happens in the next eight weeks.

What we tell every family before a screen.

Our own report template says it in its first paragraph, and we mean it: a screen "is a movement-quality screen, not a diagnosis, not a measure of fitness or talent, and not a stand-alone predictor of injury."²

Two more rules follow from that. A screen result may never be used to select, cut, or rank a child — our protocol prohibits it in writing.² And any pain during a screen ends that pattern's score and triggers a referral, not a training plan.²

At nine, thirteen, sixteen.

Nine. The most useful age for a first screen — not because nine-year-olds are at risk, but because the baseline you draw now is what every later screen is measured against.

Thirteen. Scores often drop during the growth spurt. That is expected, and our protocol says so: a drop mid-spurt is a load signal, not a failure, and the child is re-screened in six to eight weeks rather than twelve.²

Sixteen. The screen's job shifts from tracking growth to catching wear: the small asymmetries that a full-size body under full-size volume starts to accumulate.

How we use it

The Movement Screen is our entry point for every child aged eight to eleven, and part of every baseline after that. We use it for what the evidence supports — describing, comparing, and prioritizing — and we say plainly what it can't do, because a family that has been over-promised once doesn't come back.

Strength training The growth spurt

Sources

Moran, R. W., Schneiders, A. G., Mason, J., & Sullivan, S. J. (2017). Do Functional Movement Screen (FMS) composite scores predict subsequent injury? A systematic review with meta-analysis. British Journal of Sports Medicine, 51(23), 1661–1669. doi.org/10.1136/bjsports-2016-096938
Alpha-Gen Performance Lab, Youth Movement Screen — Assessment Report (protocol, ages 8–18): Purpose and Scope; Risk Flags; Longitudinal Tracking; Data handling and limitations.

All studies How much does sleep actually matter?

Science

The Energy · 01Cohort study4 min

How much does sleep actually matter?

One study, one page. A single school, 112 athletes, 21 months — and the plainest injury predictor anyone has found.

The thing nobody schedules.

Training is planned. Competition is planned. Homework, in its way, is planned. Sleep is what's left — and for a young athlete on a 5 a.m. training schedule, what's left is often not enough.

Most families treat that as the price of being serious. One study asked what the price actually was.

The study.

Researchers at a children's hospital in Los Angeles followed 112 student-athletes, aged 12 to 18, at a single school for 21 months, tracking their sport injuries alongside a survey of their sleep habits and training.¹ Over the study period, 57% of them — 64 of the 112 — were injured at least once.¹

Then they asked which factors separated the injured from the uninjured.

What it found.

1. Under eight hours, injury risk rose by 70%. Athletes "who slept less than 8 hours per night were 1.7 more likely to sustain an injury than the ones who slept 8 hours or more."¹

2. Every year older added risk on top. "Each year at school increased the risk of sustaining an injury by 1.4."¹ Older adolescents train harder, sleep less, and get hurt more — the three move together.

What it doesn't say.

It is one school. 112 athletes, self-reported sleep, a single campus. The finding is strong and has been repeated since — but this study alone describes a pattern, not a law.

It doesn't say sleep prevents all injuries. It says the under-slept body is a more breakable one. Collisions still happen.

It doesn't say "sleep more" is easy. For a thirteen-year-old with morning practice and evening homework, eight hours is a scheduling problem the adults have to solve. That is the point of the number: it moves sleep from the child's column to the family's.

At nine, thirteen, sixteen.

Nine. Sleep is still mostly protected by bedtime. Keep it that way. This is the age to make "training tomorrow means bed tonight" a habit rather than a negotiation.

Thirteen. The growth spurt, the phone, the 5 a.m. session and the exams all arrive together. This is where eight hours quietly becomes six — and where, by this study, injury risk climbs with every lost hour.

Sixteen. Training load is near adult; sleep need is not adult. The athlete who protects sleep now is the one whose body is still intact for the season that matters.

How we use it

Sleep is the first thing we look at when a body starts breaking or a plateau appears — before volume, before technique. It is the cheapest fix in the entire method and the one most often skipped. It's why the Energy ring starts with the hours when repair actually happens.

Girls at thirteen The Method

Sources

Milewski, M. D., Skaggs, D. L., Bishop, G. A., Pace, J. L., Ibrahim, D. A., Wren, T. A., & Barzdukas, A. (2014). Chronic lack of sleep is associated with increased sports injuries in adolescent athletes. Journal of Pediatric Orthopaedics, 34(2), 129–133. doi.org/10.1097/BPO.0000000000000151

All studies Why do children quit?

Science

The Spark · 01Survey + review5 min

Why do children quit?

One survey and one review, one page. What children say when they leave — and what forty-three studies say is underneath it.

The question that gets asked too late.

Most families only ask why a child quit after the child has quit. By then the answer is a shrug: "she just lost interest." The research says the losing was visible for a long time — and that it almost never looks like a lack of talent.

Source one: what children say.

In late 2025 the Aspen Institute surveyed 3,827 young people aged 10 to 17 across the United States about their sport — including those who had stopped.¹

The average age at which former players quit: 12.9.¹ Over a third of all who quit did so in a three-year window, at twelve, thirteen and fourteen.¹

Asked why, the most common answer was not injury, cost, or time. It was "I'm not good enough" — 29%.¹ The second was "bad coaching," at 21%.¹

Read those two together: half of the children who leave are leaving because of how the sport made them feel about themselves, or how an adult made them feel about the sport.

Source two: what the research says is underneath.

In 2015 two researchers reviewed 43 studies on youth sport dropout and sorted every reason they found.² Five categories held: "lack of enjoyment, perceptions of competence, social pressures, competing priorities and physical factors (maturation and injuries)."²

Their conclusion was the important part. The reasons children leave are mostly not about the sport's structure — the cost, the schedule, the distance. They are about the child and the people around them: "intrapersonal and interpersonal constraints are more frequently associated with dropping out of sport than structural constraints."²

"Perceptions of competence" is the research phrase. "I'm not good enough" is the child's.

What it doesn't say.

It doesn't say quitting is always a loss. Some children leave one sport for another, or for something they love more. The concern is the child who leaves everything, at thirteen, feeling like a failure.

It doesn't say the child is right. "Not good enough" is a belief, and the survey records the belief, not the ability. Many of the children who say it are perfectly capable. That is the tragedy of the number, and also the opening.

It doesn't say it's the parents. The review names social pressures and coaching; it does not name families. It names the feeling — and feelings can be seen early, if someone is looking.

At nine, thirteen, sixteen.

Nine. Enjoyment is the whole game. A child who is having fun is, by this research, the child least likely to leave. Nothing else at nine predicts as well.

Thirteen. The peak year for quitting, and the year the growth spurt, the first real competition, and "not good enough" all arrive together. The comparison to teammates is loudest exactly when the body is least comparable.

Sixteen. The children still here mostly stay. The ones who left at thirteen rarely come back. Whatever was going to be protected had to be protected earlier.

How we use it

"Not good enough" is the sound of the Spark going out, and it is audible months before it happens — in what a child says about themselves, and in whether the sport is still in their free time. Every month, we ask. That conversation is the whole reason the Spark ring exists.

Whose goal is it?The early winner

Sources

Aspen Institute, Project Play, National Survey of Youth and Sports, 2025 (n = 3,827, ages 10–17). projectplay.org
Crane, J., & Temple, V. (2015). A systematic review of dropout from organized sport among children and youth. European Physical Education Review, 21(1), 114–131. doi.org/10.1177/1356336X14555294

All studies Will strength training stunt their growth?