Different tissue, different failure point
In an adult, overload usually shows up as a muscle strain or a tendinopathy. In a growing child, the same overload lands on the apophysis, the growth cartilage where the tendon attaches, because that is the weakest part of the chain.
This is why adult programmes transplanted onto young athletes produce a different injury profile. The training stimulus may be reasonable; the tissue receiving it is not the same.
Different adaptation
Before puberty, low circulating anabolic hormones mean strength improves mainly through better neural recruitment rather than muscle growth. Programmes built around hypertrophy - high volume, split routines, chasing soreness, miss the point entirely at this stage.
What does work is frequent practice of quality movement with moderate loads: the nervous system learns fast, and those motor patterns persist.
Different recovery needs
- Growing athletes need 8–10 hours of sleep, and most get considerably less.
- Energy requirements include growth as well as training, under-fuelling is common and consequential.
- School, exams and social demands compete with recovery in ways adult schedules do not.
- Adolescents often recover well between sets but poorly across a congested week.
Different motivation
Adults will grind through a boring programme for a distant goal. A 12-year-old will not, and should not have to. Enjoyment, variety and visible progress are not soft extras - they determine whether the athlete is still training in two years, which is the variable that actually predicts long-term development.
What to do instead
- Build a movement vocabulary before building a physique.
- Progress through quality, range and tempo before load.
- Include jumping, landing and sprinting as trained skills, not incidental match activity.
- Plan in blocks of years, with off-seasons and varied sport.
- Adjust during growth spurts rather than pushing through them.
- Make sessions something they want to turn up to.
The one adult principle that does transfer
Progressive overload still applies. Tissue adapts to gradually increasing demand at any age. The difference is in the currency: for adults it is often kilograms, and for young athletes it is more often control, range, complexity and consistency, with load arriving later than most people expect.