PHV Maturity Tracker

Interpreting results

Pre-PHV  (offset below −1.0 year)

Steady, predictable growth. Neural development outpaces musculoskeletal development, and low circulating androgens mean large gains in muscle size are not yet available.

Priorities: motor skill development and movement quality — fundamental movement skills, landing and deceleration mechanics, change of direction, agility, coordination. Bodyweight and light-load resistance work with heavy emphasis on technique; strength gains here come largely from neural adaptation, which is genuinely trainable. Short speed exposures. Variety and play.

Avoid: chasing load or maximal testing, high-volume repetitive single-sport work, and assuming a small late-maturing child is less capable than an early-maturing peer of the same age.

Circa-PHV  (offset −1.0 to +1.0 year)

The fastest period of growth. Long bones lengthen ahead of the muscle-tendon units crossing them, producing longer levers, reduced relative strength, altered limb inertia and often a dip in coordination. Bone mineral density lags behind bone length, and growth plates and apophyses are at their most vulnerable.

Priorities: manage load rather than add to it. Track growth velocity closely. Re-teach fundamental patterns as the body changes rather than assuming mastered skills still hold. Maintain mobility — hip flexors, hamstrings, quadriceps, calves. Continue resistance training but prioritise technical quality, posterior chain and trunk control over loading progressions.

Watch for: anterior knee pain, pain at the tibial tuberosity (Osgood-Schlatter), heel pain (Sever's), pain at the inferior pole of the patella, low back pain, and any point tenderness over bone. These warrant reduced load and medical review — not coaching through.

Performance may plateau or dip here despite good training. That is biology, not effort. Tell athletes so explicitly; this is a common dropout point.

Post-PHV  (offset above +1.0 year)

Growth in stature decelerates. In boys, rising androgens drive substantial increases in muscle mass and force production; in girls, strength gains continue with a different hormonal profile.

Priorities: the window where structured strength and power training yields the largest returns. Progressive loading, heavier compound lifts once technique is sound, properly progressed plyometrics, more specific conditioning. Testing becomes more meaningful and reliable.

Watch for: injury risk shifts from bone and growth plate towards muscle and tendon — hamstrings especially in high-speed running sports.

Squad management

Bio-banding: grouping by maturity rather than age for some sessions. Early maturers are challenged against physically similar peers instead of dominating through size; late maturers get to use skill rather than being overwhelmed. An occasional tool alongside normal age-group activity, not a permanent replacement.

Relative age effect: within any 11–13 group, athletes born early in the selection year are often bigger and more developed, and are systematically over-selected as a result. Maturity data helps separate who is genuinely ahead in skill from who is simply ahead in development.

Late maturers are often under-rated and at higher dropout risk, but have a longer pre-PHV window to build skill and frequently catch up or overtake. Protect them from being cut on physical grounds. Early maturers may rely on physical dominance and under-develop technical skill — challenge them technically.

Growth velocity — the practical tool

Velocity is measured rather than predicted, which often makes it more actionable than maturity offset itself. Re-measure standing height every 6–12 weeks in this age range. Two consecutive rapid readings, combined with an athlete reporting new joint pain or a drop in movement quality, is a clear signal to reduce high-impact and high-volume work for a period. Peak velocity at PHV is typically around 8–9 cm/yr in boys and 7–8 cm/yr in girls, with wide individual variation.

Maturity timing — early, on time or late

Timing compares each athlete's estimated age at PHV with the average: about 13.5 years for boys and 11.5 for girls (Malina and colleagues found about 13.8 in boys' soccer academies). More than a year earlier than average is shown as Early, more than a year later as Late, otherwise On time.

Treat timing as a guide. The Mirwald equation pulls estimates towards the average: true early maturers tend to be predicted later than they really are, and true late maturers earlier. So a real early or late maturer is probably more extreme than the label suggests.

Growth and weight flags

A growth rate of 7.2 cm/yr or more in boys or 6.7 cm/yr or more in girls, or weight gain of 6 kg/yr or more in boys or 5.5 kg/yr or more in girls, has been linked with higher injury risk (Monasterio et al., 2024). Circa-PHV players also carry a higher injury burden than pre- or post-PHV players (Monasterio et al., 2023). Either flag is a prompt to check in and review jumping, sprinting and total volume — not a diagnosis.

How often to test, and how accurate it is

Re-check maturity every 4–6 months (2–3 times a year). The Squad data table shows Retest soon from 4 months and Retest due from 6 months. For growth velocity, standing height every 6–12 weeks is better still.

The offset is most accurate within about a year of PHV — roughly ages 12–16 for boys and 9–13 for girls, best of all around 13–15. Results outside those ages are marked with ~ as rougher estimates. Some studies use ±0.5 years for the circa-PHV band; this app uses ±1 year, the more common coaching cut-off.

% of predicted adult height (Khamis–Roche)

A second method, often more accurate than the offset in youth sport: the athlete's height as a percentage of their predicted adult height, using their height, weight, age and both biological parents' heights. The growth spurt usually starts at about 85%, PHV is at about 90–91.5%, and the circa-PHV period is roughly 88–96%. Parents' heights you measure yourself are better than reported ones, which tend to be over-estimated.

Boundaries

This tool supports coaching decisions about grouping and workload. It is not a medical tool. Predicted adult height is used only to work out the percentage of adult height reached — don't share it as a prediction, and don't use any of these numbers to select or de-select athletes or to diagnose anything. Avoid sharing individual maturity results with athletes in a way that reads as a verdict on their potential. Persistent pain, concerns about growth, and questions about nutrition or body composition in this age group belong with a qualified medical professional. Follow your club's and governing body's safeguarding policy for recording data on minors, get parental consent, and share this data only with those who need it.

Mirwald equations carry a standard error of roughly ±1 year and were derived from a longitudinal sample of white Canadian youth; accuracy degrades at the extremes and may be lower in other populations.

Sources: Mirwald RL et al. An assessment of maturity from anthropometric measurements. Med Sci Sports Exerc 2002;34(4):689–694 · Khamis HJ, Roche AF. Predicting adult stature without using skeletal age: the Khamis–Roche method. Pediatrics 1994;94:504–507 (erratum 1995;95:457) · Monasterio X et al. Biology of Sport 2024;41(1):235–244 · Monasterio X et al. Int J Sports Med 2023;44(4):292–297 · Malina RM et al. Ages at peak height velocity in male soccer players 11–16 years, Biology of Sport · Retzepis N-O et al. J Funct Morphol Kinesiol 2025 · Science for Sport, "Peak Height Velocity" · RYPT, "What is Peak Height Velocity" · Sportsmith, Johnson & Kite, "Calculating maturity overcomes the bias towards early-developing youth athletes".