The Just Jump System pioneered field jump testing, but it over-reports flight time by a fixed factor — so 30 years of jump heights have read high. Enter a Just Jump number below to see the real value, then see how Plyomat keeps you accurate and cross-compatible.
A contact mat figures out jump height from flight time — how long the athlete is in the air — using simple projectile physics. The original Just Jump System applied a built-in flight-time factor of roughly 1.1119. Plyomat verified it directly with an oscilloscope: the displayed flight time runs about 11% long.
Here's the catch most coaches miss: jump height scales with flight time squared. So a ~11% flight-time inflation compounds into roughly a 24% (×1.236) inflation in displayed jump height — commonly 4 to 7 inches. That's not a knock on the hardware; the Just Jump is a consistent timer. It just means the absolute numbers a generation of athletes grew up with were systematically high.
Plyomat measures the truth — and includes a Just Jump mode that can re-apply the 1.1119 factor on purpose, so your historical numbers stay continuous when you switch. Leave it on for continuity, or turn it off to see real height. Either way you also get contact time, RSI, RSQ, and Power Score the original never reported.
| Capability | Just Jump System | Plyomat |
|---|---|---|
| Jump height | Inflated ~24% (×1.236) | Accurate (force-plate validated, r≈0.97) |
| Ground contact time & RSI | No | Yes (0.001 s) |
| RSQ, Power Score, asymmetry | No | Yes |
| App, rosters, reports | Handheld display only | Free app, no subscription |
| Connectivity | None | Bluetooth (iOS/Android/web) |
| Keep your historical numbers | — | Yes (Just Jump mode) |
| Mat compatibility | Just Jump controller | Same M8 connector — cross-compatible |
Plyomat switch mats use the same M8 connector as Just Jump controllers, so the migration is a swap, not a rebuild.
Contact time, RSI, the Reactive Strength Quadrant, and Power Score — timed to 0.001 s. Far more than a single jump height. See RSI →
Just Jump mode re-applies the old inflation so longitudinal data stays continuous — or switch it off for the true number.
Upgrade from the Just Jump System without relearning a thing — cross-compatible mats, accurate data, a free app, and a Just Jump mode that keeps your history intact.
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