Youth athletes

At what age do we start testing children — and why it is not talent selection

360 Ergometric Tests · Sports Science Lab, Nicosia, Cyprus · August 2026

It is one of the questions we hear most often — from parents and from coaches alike: “when is it too early?” The answer is that the question is put the wrong way round. There is no magic age. There is which measurement, at which stage of maturation, and which decision it will change. Judged by that criterion, testing starts far earlier than most people think — but for a completely different reason than the one they imagine.

The short answer

We start at around 6–8 years with anthropometry and simple field tests. Laboratory tests (cardiopulmonary exercise testing, isokinetic assessment, resting metabolic rate) come in after the growth spurt. And the purpose, all the way through, is not to work out which child “has talent”, but to build each child's own curve — because without it, every number we get at 14 will be misleading.

6–9 years — the baseline

Anthropometry (stature, weight, sitting height, skinfolds), motor competence and simple field tests: jumping, 10 metres, agility, flexibility. They take very little time, they feel like a game, and the child learns the routine. The purpose here is threefold: growth monitoring, familiarisation (a child who has been tested before gives a far more reliable measurement the next time) and motivation. No selection, no ranking.

9–12 years (Pre-PHV) — before growth kicks in

We add the CMJ jump, handgrip dynamometry, 10/20/30 metre sprints and aerobic field tests. This is the most critical phase, for a very practical reason: the baseline has to exist before growth arrives. If a child's first test happens at 13, we will never know whether the improvement we see came from training or simply from ten extra centimetres of height.

Around PHV (~11–13 girls, ~12–14 boys) — this is where we test more often

The intuitive move is to test less often “because everything is changing”. That is exactly the wrong move. During peak height velocity a child goes through a period of temporary awkwardness, loses flexibility, the bones grow faster than the muscles and the tendons pull on the apophyses — which is where the Osgood-Schlatter and Sever cases that every academy coach knows come from. Here we measure stature every three months and run the full battery three times a year. Measurement at this stage is not assessment; it is load management.

Post-PHV (~14+) — now for the laboratory tests

After peak growth, cardiopulmonary exercise testing (VO₂max, thresholds, zones), isokinetic assessment, resting metabolic rate measurement and anaerobic protocols start to make sense. Before that, absolute values mislead — a child who has grown 8 centimetres will “improve” in almost any test without having trained any better.

Why — four reasons, in order of importance

1. Maturation is the biggest confounder

Two children born in the same year can be three or four years apart in biological age. If you compare their performances without taking that into account, you are not measuring ability — you are measuring how early they matured. And because the system selects on the basis of what is visible today, early maturers get picked and late maturers drop out, often while they were the more capable of the two. That is why in our reports every value is accompanied by a maturity offset — an estimate of how far the child is from PHV, derived from anthropometric equations (Mirwald et al. 2002; improved version Fransen et al. 2018). We measure early and repeatedly precisely in order to correct that bias, not to feed it.

That this is not just theory is shown by the practice of bio-banding — grouping by maturation instead of chronological age. In a randomised study in football academies (Lüdin et al. 2021), when children played in maturity-matched groups, the late maturers produced significantly more balls won and more attacking actions — that is, they showed technical and tactical qualities that simply never had the chance to appear in the regular league — while the early maturers faced a greater physiological challenge. The abilities were there; the categorisation was hiding them.

2. Injury prevention in the growth window

Growth velocity is a measurable quantity — and on that basis you can intervene before the damage is done. In a football academy (Johnson et al. 2023), the sports science staff identified the “high-risk” children using three criteria — 88–92.8% of predicted adult stature, a stature growth rate of ≥7.2 cm/year and ≥3.6 cm/year in the lower limbs — and gave them modified loading, balance, coordination and landing drills, and an individualised strength programme. In the children who met all three criteria, injury incidence fell to 14% and injury burden (days lost) to 8% compared with the previous season. Without measurement, those children are simply never identified.

Along the same lines, a study of 400 young academy footballers (Read et al. 2018) showed that between-limb asymmetries appear around PHV — in the U14–U15 age groups and in the circa-PHV group — and decrease later on. It is, in other words, a transient but real window of risk, one that only becomes visible if you are looking at exactly that period.

3. Individualisation instead of generic recipes

Before puberty, the biggest improvements come from neural adaptations — agility, balance, coordination — and not from muscle hypertrophy, which plays the leading role later on (Walters et al. 2017). The same paper notes that strength training in children, when done properly, reduces injury risk, whereas early specialisation in a single sport increases it. Measurement is what shows where each child is along that path — instead of handing ten-year-olds the sixteen-year-olds' programme in a smaller dose.

4. The child sees their own progress

The last reason is the most underrated one. When a child sees their own curve — “last September you ran the 20 metres in this time, now you run it in that” — the comparison is with themselves and not with the child next to them. That is the kind of motivation that lasts; a ranking is not.

What we do NOT do — equally important

How often

Twice a year as a minimum; three times around PHV, with stature recorded every quarter. In practice that translates into the cycle we run with our teams: mid-September (pre-season baseline) — January (mid-season) — May (end-of-season review). Three measurements a year are enough to see a trend and few enough not to become a burden.

For parents: what to ask

And one reassurance: the tests we run on children of these ages are submaximal, non-invasive and safe. There is no needle, there is no exhaustion, and the child can stop whenever they want. They are always carried out with the parent's consent and the child's own assent.

For coaches and academies: the practical protocol

The bottom line

We test children early not in order to judge them, but in order to have the history that will allow us to judge them fairly later on — and in order to protect them during the phase when they are most vulnerable. The measurement taken at 8 says nothing on its own; it says everything when you see it next to the one at 11 and the one at 14.

In our lab, children's measurements are recorded on the platform with a maturation profile and age norms, so that parents and coaches see the trajectory and not a snapshot. See also the related articles on PHV and biological maturation and on strength as a means of prevention.

References

Source of bibliographic references: PubMed. This article is for information purposes and does not replace medical advice.

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