Discovering inflation

In the early prototyping days of 2020, we noticed right away that jump heights on our first Plyomat were significantly lower than those from the popular Just Jump System.

So we did what any data-obsessed coach-engineer would do: we put both on an oscilloscope. An oscilloscope further proved that the Just Jump Controller was measuring flight times that were, on average.05–.08s longer than what we validated with the first Plyomat.

That difference in flight time resulted in about a 4–7 inch higher jump. Same athlete, same jump, two very different numbers, simply because of how each device timed the air.

.05–.08s
Extra flight time read by the Just Jump controller
4–7″
Resulting jump-height inflation
2020
When we first caught it on the oscilloscope

Why the inflation?

We can only speculate as to why the Just Jump Mat, created by Paul Mackovjak in 1991, has this inflation baked in.

My personal theory is that it was added intentionally to match numbers recorded by older devices such as the Vertec, making it more valid and marketable at the time. Even research in the early 2000s studied its similarity to the Vertec, and it held up well against that criterion.

McMahon, Jones & Comfort (2016)

Re-examined the Just Jump against a force plate and confirmed that the system overestimated jump height by roughly 0.13 m.

Leard et al. (2007)

Compared the Just Jump and Vertec to a three-camera motion-capture system. Both correlated highly with the criterion, r = 0.967 for the Just Jump.

So the device is reliable and well-correlated, it just reads consistently high.

"The major issue is that it gave everyone the assumption that ALL switch-mat technology is inflated.

Legacy data and standards

Here's the bind. Like many of the other thousands of coaches who have used the Vertec and Just Jump Mat, I had been testing athletes according to standardized data from these inflated devices for years. Twenty years of records, norms, and athlete history, all calibrated to numbers that run high.

Thus, I had to make a decision about keeping the inflation. Switch every athlete to "true" numbers overnight and watch a roster of personal bests appear to drop 4–7 inches? Or build a bridge?

The Just Jump calculation

Every switch mat converts flight time to height using the same physics:

Flight-time to height
h = (g × t²) ÷ 8
where g = gravity, t = flight time

Because the Just Jump's firmware lengthens t, we reverse-engineered the scale factor that would recreate its results:

Just Jump scale factor
t(Just Jump) = 1.1119 × t(Plyomat)

In other words, Just Jump Mode doesn't guess, it applies a precise 11.19% multiplier to flight time so that a Plyomat reproduces legacy Just Jump numbers exactly. Here's what that looks like on a real jump:

Parameter Plyomat Mode Just Jump Mode Difference
Average flight time 0.505 s 0.562 s 11.19%
Reported jump height 24.8 in 29.2 in +4.4 in
Purpose Precision Continuity ,
"Just Jump Mode preserves historical data, while Plyomat Mode aligns with force-plate standards.

Rationale for the mode

This isn't just my hill to die on. It's a sentiment shared by coaches who've built decades of athlete history on these numbers.

Coach Mike Boyle

"Data only matters if it's comparable. I don't care how advanced the new tech is; if it breaks continuity with the standards we've been using for 20 years, it's useless. That's why I like what Plyomat did with Just Jump Mode. It lets you move forward without losing the historical context and preserves the positive athlete atmosphere."

Making the decision

So which mode should you run? It comes down to what you're trying to protect, precision, continuity, or the ability to compare across systems.

Situation Best setting Rationale
Starting a new testing program Plyomat Mode Matches force-plate data
Maintaining a multi-year Just Jump database Just Jump Mode Preserves continuity with past records
Comparing different facilities or technologies Conversion sheet Normalizes all data to a single standard

Coach takeaway

Keep in mind, Just Jump Mode only affects Vertical Jump values. By default, every controller ships with it disabled, but it's very easy to toggle on or off directly on the controller or via the mobile app.

The point of building it wasn't to hide a flaw, the Plyomat measures flight time precisely. The point was respect: respect for the thousands of coaches whose 20-year databases and athlete relationships are calibrated to the old standard. New tech shouldn't force you to throw that away. Run Plyomat Mode when you want force-plate-aligned precision, run Just Jump Mode when you need continuity, and use the conversion sheet when you need to speak both languages at once.