Prescribe by maturity, not by age

A single Under-14 squad holds boys who have not yet hit their growth spurt alongside boys already past the peak. The JFA estimates maturity offset from height, weight, sitting height and chronological age, sorts players into four bands, and specifies a different kind of loading for each. It is not an age-group program; it is a maturity-stage program.

Power climbs a three-step ladder

Base power, then conversion power, then football power. The middle step — moving weight-room strength into match actions — is named and deliberately timetabled rather than assumed. Only at maturity phase 4 are all three run together.

Testing is a feedback tool, not a selection tool

The JFA states plainly that assessing development-age players is difficult because they develop at different rates. The published national-squad averages are one target among several, not a cut-off. In the 2021 data the Under-18 squad's countermovement jump ran from 53.1 cm down to 37.7 cm — a 15.4 cm spread inside one squad.

A settled protocol matters more than the data

The 2021 national-squad testing used a three-point start with one hand on the ground; the 2023–2026 National Training Centre data used a standing start 30 cm behind the gate. Change the start alone and the two datasets stop being comparable. The JFA recorded the difference in a footnote rather than quietly merging the numbers.

Running data is a function of match context, not fitness

When the opposition drops into a back five, both distance covered and sprint count fall with it. Judge a player's work rate on GPS numbers alone and you will misread them. Every JFA GPS report describes the opponent's shape and the fixture schedule alongside the figures.

Almost nothing is done away from the ball

Even the return-to-play aerobic work is built as a sequence: scanning while running, then dribbling, then pass and move, then pass and control, then fisico-tecnico. Intensity is steered by heart rate, by percentage of top speed, and by the coach's signal.

The first lever is food, not training

Having published BMI targets by age group, the sentence the JFA attaches underneath is that reaching them depends on what a player eats every day. Players yet to hit the growth spurt will read low on the scale regardless, so what is being built at that age is not a body but an eating habit.

A small expert group plus a coach-education network

The project runs on roughly twenty people nationally. They do not meet every player; they reach working coaches through licence courses, refresher seminars, academy-staff seminars for J.League clubs, and published material. Anyone importing this model should study that delivery structure before copying a single drill.

09

Injury prevention and training content

Sixteen hamstring exercises, fourteen mini-band exercises. The order of the list is itself a difficulty ladder, and where each item sits in the session is the prescription.

10

Programming principles and coach education

Intensity is steered by heart rate, by percentage of top speed and by the coach's signal. And every menu carries the same rider — watch the player's condition and adjust.