// methodology · in the open
The Development Index,
with nothing hidden.
Most places in youth baseball sell a black-box number or a scary injury claim. We do the opposite: here's exactly how our Development Index is built, from an athlete's own logged data — and, honestly, what it does and doesn't mean.
A development-trajectory score — not a medical or scouting grade.Four pillars, real weights
The Index is a 0–100 composite of four transparent pillars. These are the actual weights our software uses — no marketing rounding.
Velocity
How much the arm has climbed over the logged span — progression, not a one-day radar number. A flat elite arm scores lower here than a kid steadily adding mph, because this is a growth score.
Arsenal
How many distinct pitch types the athlete has developed and thrown. A four-pitch mix reads as a fully built young arsenal.
Arm safety
Workload headroom from our multi-factor arm read (volume, velocity trend, intensity spikes, rest). This is workload monitoring — not a clinical injury prediction.
Track record
How long the athlete has been verifiably logged, and how consistently. Months of real, coach-logged history — the thing a snapshot can't fake.
What the number means
Because it rewards *trajectory*, the Index climbs as an athlete logs more, adds velo safely, and broadens their arsenal — it's a picture of development over months, which is exactly what a single-day scouting number can't show.
What we don't claim
- It is not an injury predictor. The Arm-safety pillar is workload monitoring— a signal to space hard days and add recovery — not a clinical risk score. No app can promise an arm won't get hurt.
- It is not a scouting grade. It measures how an athlete is developing on their own curve, not where they rank against a draft board.
- It only knows what's logged.The Index is honest about its inputs — the more real sessions and throws are recorded, the sharper it gets, and it says so when it doesn't have enough data yet.
The science we build on
We'd rather tell you where the evidence is solid and where it's genuinely uncertain than pretend it's all settled.
- Pitch counts reduce youth injury but are inadequate alone — velocity and intensity spikes are independent risk factors (HS cohort, 10.1177/03635465241246559).
- Higher velocity means more elbow torque and UCL stress (PMID 36649827) — so we celebrate velo gained inside a safe workload, not velo at any cost.
- Weighted-ball programs raise velocity and injury rate (RCT, PMC7930148) — we surface the trade-off instead of hiding it.
- The ACWR "safe zone" is contested and adult-derived — a monitoring signal, not a validated youth injury-prevention rule (Sports Med review, 10.1007/s40279-020-01308-6).
See a real athlete's Index
Book a first session — velo, arsenal, and arm read logged on day one.