Early and late developers
Evidence: moderate
Some athletes rise fast early and plateau; others develop slowly and reach a higher ceiling. Junior success is a weak predictor of senior success, partly because early advantage is often maturation rather than talent. The practical lessons: do not over-read youth results, do not specialise or deselect early, and be patient, the slow developer is not the failed one.
Athletes do not develop on a single timetable. Some are “fast risers”, improving quickly as juniors and then levelling off; others are “slow bakers”, developing gradually over years and reaching a higher final level than their early results suggested. The mistake, made by selectors and self-coached adults alike, is to treat the early trajectory as destiny.
Junior success poorly predicts senior success
The data are clear that winning young does not reliably translate into winning as an adult. Most junior champions do not become senior champions, and a large share of senior elites were not standout juniors. A major reason is the relative age effect: in age-group sport, children born early in the selection year are bigger and more mature, so they dominate and get picked, an advantage that looks like talent but is mostly months of extra growth. Strikingly, this effect reverses on the way up. In world-class track and field, the relatively younger athletes, those disadvantaged as juniors, had higher junior-to-senior transition rates and a better chance of reaching and holding senior elite level (Brustio, Stival & Boccia 2023).
Why the early advantage fades
The reversal makes sense once you separate maturation from ability. The early developer’s edge, size, strength and an earlier growth spurt, is temporary; everyone matures eventually, and the advantage evaporates once the field catches up physically. The late developer who stayed competitive without that physical head start was, in effect, more skilled or more trainable all along, and may also have developed more durable technique and motivation by having to compete from behind. Meanwhile the early star can be harmed by early success: pushed into early specialisation and heavy training before the body is ready, with the raised injury and burnout risk that brings.
What it means in practice
- Do not over-read youth results. A schools or junior result, good or bad, says little about adult potential. Selecting and deselecting hard on early performance discards late developers who would have been better seniors.
- Avoid early specialisation. Broad, playful, multi-sport development beats narrow early specialisation for long-term outcome and health; the case is set out under youth and adolescent runners.
- Be patient as an adult runner too. The slow-baker pattern is reassuring for the late starter and the steady improver: distance running rewards years of accumulated consistent training, and trainability is individual, so a slow, durable climb often beats a fast early peak. Masters performance shows how long the runway really is.
The same shape, fast risers who fade and slow developers who overtake them, recurs well beyond running, in talent development generally. This page keeps to athletes; the general principle is noted only to say the pattern is not unique to sport.