The Rise of the Teenage Superstar: Why Growth Spurts Are the Real Danger Zone

Part four of my world cup series

On 5 July, Norway did what no team had managed since 1990: they ended Brazil’s World Cup at the Round of 16, winning 2–1 behind an Erling Haaland masterclass. For the first time in World Cup history, neither Brazil nor Germany reached the quarter-finals. It was a genuine shock — and it happened to a Brazil side built, in part, around teenagers.

This tournament has been billed as the coronation of the “Young Guns.” Lamine Yamal, still a teenager, leads every player at this World Cup for take-ons completed and will carry Spain into their quarter-final against Belgium. Brazil turned to Endrick when Lucas Paquetá tore his hamstring in the Round of 32, and they were already without Estêvão, who suffered a grade four hamstring strain back in April.

Whatever happens in the knockouts from here, the story of this tournament is being written by players who, in a normal week, would still be doing their GCSEs (or maybe lounging around after having just finished them).

Behind the technical brilliance, these players are navigating the most perilous window of their physical development: the somatic growth spurt.

The Science: The 7.2cm Threshold

Chronological age is a poor predictor of injury risk in youth football, because players of the same age can have skeletal ages that differ by five to six years. If you want to protect young talent, stop looking at the date of birth and start looking at growth velocity.

The definitive danger zone is a growth rate of 7.2cm per year or more — 0.6cm per month. This is Peak Height Velocity, or PHV. When a player enters this phase, coordination is often temporarily disrupted — “adolescent awkwardness” isn’t a throwaway phrase, it’s a documented phenomenon — and the tissues are under real mechanical stress.

Picture a piece of plasticine rolled out on a table: it gets longer, not stronger. Any coach or parent of teenagers will recognise the pattern.

Circa-PHV vs Post-PHV

Injury risk doesn’t arrive in one wave — it shifts as a player matures.

1. Circa-PHV (the peak of the spurt): the highest-risk window for growth-related injuries like Osgood-Schlatter or Sever’s disease. Bones are growing faster than muscles and tendons can lengthen.

2. Post-PHV (the mature academy player): once the spurt slows, risk shifts to soft-tissue injuries — muscle, ligament, tendon strains. Early maturers are significantly more prone to these than their on-time or late-maturing teammates.

My son playing earlier this year: a late-developer, but stronger than he looks.

Building the Foundation

Before we apply The Sprint Vaccine or The Sleep Gap to academy players — and for a growing athlete, that 1.3-hour sleep deficit matters even more, because deep N3 sleep is when the growth hormone required for tissue repair is released — we need to get the strength training right.

One of the key tenets at our club is: Long and Strong (credit to Steve Myrland for the phrase). Forget what your favourite influencer is doing in the gym to chase “gains” — usually a re-hashed bodybuilder’s programme — and think control, technique, and balance instead. Or, as Frans Bosch puts it: coordination training with resistance.

Lying on a bench pressing weight above your chest will make your chest bigger. Well done. Sitting on a leg extension machine piling on plates to “feel the burn” will make your legs sore. Well done. But football — like most sport — is played standing up, on one leg, far more often than either of those exercises ever accounts for.

At Excelsior, our Athletic Development sessions are built around that reality: develop the athlete first, and the sport-specific application follows on the pitch:

Three things to do this week

1. Monitor monthly. Take height measurements every month. A jump of more than 0.6cm is your signal to modify load — not a coincidence to ignore.

2. Adjust the load, and train the full range. During the danger zone (7.2cm/year or more), cut high-impact jumping and explosive change-of-direction work by 20–30%, and build strength from fingernails to toenails rather than chasing one or two gym lifts.

3. Educate the stakeholders. Coaches and parents both need to understand that a dip in performance during a growth spurt is usually physiological, not a drop in effort. Tell them before the spurt happens, not after someone’s already been benched for it.

That’s the final post in this World Cup series. Four posts, four windows into the same idea: the margins in performance sport are won and lost in preparation most people never see — the hydration and energy balance in Mastering the 98%, the sprint exposure in The Sprint Vaccine, the recovery debt in The Sleep Gap, and now the growth window that decides whether a talented teenager makes it through to the level Yamal, Endrick, and Estêvão are playing at right now.

Whoever lifts the trophy on 19 July, the players worth watching over the next four years are the ones being coached properly through this exact stage today.