Research · Long-Term Athletic Development

Pre-PHV, Circa-PHV, Post-PHV: What to Actually Train at Each Stage

By Muhammad Dzulhisham · MSc Sports Coaching, NSCA-CSCS

Ask most coaches what the research says about training young athletes and they'll mention the same two headlines: don't specialize too early, and forget the 10,000-hour rule. Both are well supported, and both answer a question about whether to train a certain way. Neither answers the question a coach actually has to solve every single session — a 9-year-old and a 15-year-old are standing in the same gym, biologically different animals, and the program has to reflect that. The peer-reviewed literature has a specific, practical answer to what belongs in each of their programs, and it's organized around a marker most parents have never heard of: peak height velocity.

The marker that matters isn't a birthday

The framework behind this breakdown is the Youth Physical Development (YPD) model, published by Rhodri Lloyd and Jon Oliver in the Strength and Conditioning Journal in 2012¹. It was built to replace an older, more rigid framework that had dominated youth coaching for years — a "long-term athlete development" model built around fixed "windows of opportunity" for each fitness quality, where missing a window supposedly capped an athlete's ceiling for good. Lloyd and Oliver's own reading of that theory is blunt: it is "largely theoretical" and "lacks supporting longitudinal empirical evidence"¹. In its place, the YPD model organizes training priorities around peak height velocity (PHV) — the point of maximum growth rate during the adolescent growth spurt — rather than chronological age.

On average, girls begin their adolescent growth spurt around age 10 and reach PHV around age 12; boys begin around age 12 and reach PHV around age 14¹. Despite hitting it two years earlier, girls' growth spurts are smaller in magnitude than boys'¹. These are averages, not rules — an early maturing child can be developmentally well ahead of an "average" peer born in the same year, which is exactly why the model is built around biological stage rather than birth certificate.

Pre-PHV: building the vocabulary before the sentence

Before the growth spurt begins, the model's priorities are fundamental movement skills (FMS) and strength, trained together rather than sequentially. The NSCA's 2016 position statement on long-term athletic development explains why: it is "optimal to target the development of motor skills and muscular strength at a time when the corticospinal tissue in children is highly 'plastic,'" and the two should be treated as "synergistic components of motor skill performance," not developed in isolation².

• Fundamental movement skills — running, jumping, landing, throwing, catching, changing direction — get the largest-font, highest-priority billing in the model at this stage, with the emphasis on FMS running right up to the onset of puberty before sport-specific skill work takes over¹.
• Strength runs alongside FMS work, not after it. The model marks strength as a bold, high-priority component at literally every stage of development it maps, from early childhood through adulthood — it is never the quality that gets switched off¹. Before puberty, those strength gains come almost entirely through neural adaptation rather than added muscle mass.
• Formal resistance training is appropriate from around age 6–7, once a child has the emotional maturity to follow instruction and adequate balance and postural control. Before that, from birth to roughly age 5–6, the recommended content is exploratory, deliberate play — climbing, crawling, gymnastics-style bodyweight work — that builds the same foundational strength and coordination without a formal training structure².
• Mobility gets its single most important development window here: the model identifies middle childhood, roughly ages 5 to 11, as the priority period for building range of motion, with adolescence and adulthood shifting to maintenance rather than active development¹.
• Speed is trained through plyometrics, technical sprint competency, and sprint work itself — methods that rely on high levels of neural activation, which is exactly what a prepubescent nervous system responds to¹.
• Agility is developed here too, starting with more closed, prescribed drills that reinforce coordination and change-of-direction technique against a body whose limb lengths aren't yet changing rapidly¹.

Training structure at this stage is deliberately loose. The model labels early childhood "unstructured," moving to "low structure" through middle childhood¹ — plenty of variety and play-based delivery, not a periodized block plan borrowed from an adult program and scaled down.

Circa-PHV: the awkward middle

The years around the growth spurt itself are where a lot of programs quietly go wrong, because the athlete's limbs are lengthening faster than their motor control can keep pace. The model has a specific term for this: rapid gains in limb length during the adolescent growth spurt "can lead to decrements in motor control performance, a concept commonly referred to as 'adolescent awkwardness'"¹. Skills that looked automatic six months earlier — a cutting pattern, a landing, a throwing motion — often need to be deliberately re-coached, not because the athlete regressed, but because their levers changed shape underneath the skill.

The paper gives a concrete illustration of how much the emphasis shifts inside just one or two years: it states that a 12- to 13-year-old boy "should primarily focus their training on strength, power, speed, agility, and sport-specific skill development, with a reduced focus on hypertrophy, mobility, fundamental movement skill (FMS), endurance, and metabolic conditioning"¹ — a genuinely different priority list than the one governing the same boy three years earlier.

• Sport-specific skill training increases sharply from the onset of puberty, building on the FMS foundation laid earlier rather than replacing it — FMS work doesn't disappear, it just stops being the main event¹.
• Agility training gets more demanding here: the model recommends progressing toward more open, unplanned drills that force reactive decisions, rather than the closed, prescribed patterns used earlier, so the training stimulus keeps overloading the athlete as they mature¹.
• Speed training shifts mechanism, not just volume — the model recommends adolescents add strength training to the plyometrics and sprint work that dominated the pre-PHV years, to target both the neural and structural adaptations now available¹.
• Power development formally starts climbing here, as the key period for power development the model identifies begins at the onset of adolescence¹.
• Hypertrophy-focused training starts to appear — the model places its onset around age 14 in boys and age 12 in girls, tracking the point where circulating testosterone and growth hormone begin rising with the growth spurt¹.
• Training structure steps up from "low" toward "moderate" and then "high" as the athlete moves through this window — this is where a genuinely periodized structure starts to earn its keep, rather than before it¹.

This stage also carries a documented, sex-specific risk. As the growth spurt progresses, female athletes develop specific movement changes — increased knee valgus angle and a more quadriceps-dominant landing strategy among them — associated with elevated noncontact ACL injury risk. The model's response isn't to pull female athletes out of strength training; it's the opposite. Plyometrics, core strengthening, strength training, and balance and perturbation training are the specific tools it recommends to counter that risk, and it recommends keeping them in the program from this stage into adulthood¹.

Post-PHV: the hormonal window opens

Once the growth spurt has passed its peak, hypertrophy work — already introduced around age 12–14 — becomes a genuine training priority rather than a minor addition, running alongside continued strength, power, and now-dominant sport-specific skill work. Endurance and metabolic conditioning also get more programmed attention at this stage than at any earlier one, even though the model is explicit that neither is ever meant to be the main focus of a session at any stage of development¹. Training structure by this point has climbed to "high," continuing toward "very high" as the athlete moves fully into adulthood¹.

The clearest evidence for why the training method itself should change here, not just the volume, comes from a meta-analysis the NSCA statement cites on sprint-speed training in male youth: boys who had not yet reached PHV made their biggest sprint improvements from plyometric training alone, while boys who had already reached PHV responded more favorably to combined strength-and-plyometric training². The statement's own explanation is that plyometric training alone reproduces the neural adaptations already happening naturally before puberty, while combined strength-and-plyometric work is needed to stimulate the neural and structural adaptations that only become available once the growth spurt has passed². Same underlying qualities — speed, power — trained through a different mechanism, because the athlete's physiology is genuinely different, not because a window has slammed shut on the old method.

What "windows of opportunity" actually gets wrong

It's worth being direct about a common misreading of this literature, because it shapes how a lot of youth programs are marketed. The older LTAD model's "windows of opportunity" theory implied that a child who missed the window for, say, speed development would carry a permanently lower ceiling for life. The 2016 NSCA position statement addresses this directly, stating that the windows-of-opportunity concept "has since been challenged largely because of a lack of supporting longitudinal empirical data," and that the accumulated pediatric training literature instead shows "both children and adolescents can make worthwhile improvements in all components of fitness irrespective of their stage of development"².

The rapid gains in limb length during the adolescent growth spurt can lead to decrements in motor control performance — a concept commonly referred to as "adolescent awkwardness."

The evidence-supported version of this idea is narrower, and more useful, than "train it now or lose it forever." The NSCA statement calls it "synergistic adaptation": certain training modes produce a bigger response at certain maturational stages because they complement what the body is already doing physiologically — plyometrics before PHV, combined strength-and-plyometric work after it — not because the underlying quality becomes untrainable outside that stage². A program that misses a stage isn't wasted. It's just working with fewer physiological tailwinds than it could have had.

Why this changes how a program should actually be built

Two practical consequences follow directly from all of this, and they're the ones that actually change what happens in a session:

• Group by maturity, not birth year. Two 13-year-olds on the same team can be genuinely different training subjects — one may already be past PHV, the other not yet into their growth spurt. The model is explicit that its stage boundaries should shift earlier for an early-maturing athlete and later for a late-maturing one, rather than staying fixed to chronological age¹.
• Training age matters as much as body age. An adult-sized 16-year-old who is brand new to structured training should still start with the model's introductory content — FMS consolidation and foundational strength — rather than being placed straight into a post-PHV program because of their size. Conversely, an early-maturing 10-year-old already showing strength, speed, and technical competency beyond their peers shouldn't be capped at introductory content simply because of their birth year¹.

None of this replaces a coach's judgment with a lookup table. The model itself is presented as a description of an "average" maturing child, with the explicit expectation that it gets adjusted for the athlete actually on the floor. What it does replace is a genuinely common mistake — running every athlete on a program keyed to their age in years — with the variable that the underlying physiology actually responds to: where they are in the process the growth spurt describes, not how many birthdays they've had.