What is “Just Jump” Mode?

Understanding the Legacy, Inflation, and Ongoing Use of the Just Jump Mat

In the realm of athletic performance testing, few devices have been as influential—or as debated—as the Just Jump Mat by Probotics, Inc. First introduced in the early 1990s, this contact-based jump testing device became a staple in strength & conditioning facilities, PE departments, and private gyms across the country.

For decades, it was the only commercially available switch mat for testing vertical jump. It was portable, simple, and consistent—traits that made it indispensable for coaches tracking athlete development over time.

However, with modern tools like Plyomat and force plates now available, many have begun scrutinizing the accuracy of the Just Jump Mat, particularly when comparing flight times and jump heights. This is where the concept of “Just Jump” Mode comes in.

What Is “Just Jump” Mode?

“Just Jump” mode refers to a setting in the Plyomat that matches the vertical jump height with the higher output of the Just Jump controller.

Many side-by-side validations—using modern switch mats, force plates, and even an oscilloscope to detect signal timing—have confirmed that the Just Jump system consistently overestimates flight time by 0.06–0.08 seconds. This results in jump heights being inflated by 4–7 inches compared to modern, validated systems.

It’s important to note that the Just Jump calculates jump height the same way as other switch mat technology (shown below); however, there is specific inflation added to it’s firmware. Plyomat was able to discern this inflation and add it as a feature within the app to toggle it on or off if the user wishes to do so.

How switch mats calculate jump height: Flight time is detected the moment both feet leave the mat and return, with an actuation force of about 15-20lbs to trigger the plates inside the switch mat to touch and produce a signal. Like all switch mat technology, the physics equation below translates that flight time into vertical jump height.

Why Is the Just Jump Data Inflated?

One prevailing theory within the coaching and biomechanics community is that the original firmware was intentionally “calibrated” to align with Vertec scores—the dominant method of jump testing prior to contact mats.

The Vertec involves an athlete reaching up to displace plastic vanes. It naturally includes a margin of visual estimation error (arm reach, body lean, etc.), and often yields higher jump readings than flight-time-based methods.

To help coaches transition to a more convenient, electronic testing tool without disrupting their existing benchmarks or recruiting standards, the Just Jump system may have been purposefully designed to mimic the higher numbers coaches were used to seeing with the Vertec. In doing so, it maintained user confidence and preserved continuity with historical data.

The Value of Just Jump Mode: Reliability Over Accuracy

While not technically accurate, the Just Jump controller is still reliable. This means:

• If an athlete scores 29.0 inches today and 31.0 inches next month, their progress is legitimate—even if their true jump heights are lower.
• The device measures change consistently, making it valuable for monitoring adaptation, motivating athletes, and comparing athletes within a program.

This is why legendary strength coaches like Mike Boyle, who used the Just Jump Mat for over 20 years, still prefer the “Just Jump number” when communicating with athletes. Boyle and others acknowledge the inflation—but find the higher number more relatable, more motivational, and still useful within context.

“I still call it a 30-inch jump if it’s on the Just Jump mat… because that’s the number that means something to the athlete and to our standards.”

— Coach Mike Boyle

Why Coaches Use It

Here are key reasons why “Just Jump Mode” continues to have a place in sports performance:

✅  Legacy Data

Most programs have decades of stored data using Just Jump. Switching to a new system with different baselines can make long-term comparisons difficult. Plyomat does provide users with a conversion spreadsheet though to convert all user data to Plyomat data or vice-versa. Link to spreadsheet.

✅  Consistency

Even if inflated, the numbers are consistently inflated. That makes them trustworthy for relative progress tracking.

✅  Athlete Motivation

Telling an athlete they have a “30-inch vertical” means something. Deflating that to 25 inches for the sake of technical purity can hurt morale—especially if their recruitment depends on it.

Should You Enable it in Plyomat Settings?

If you’re just getting started, building a high-performance model, or preparing athletes for combines where force plates or newer tech will be referenced, then no—starting with accurate data makes sense.

But if you’re already 10 years deep into a dataset of Just Jump scores and simply want to measure training response, then yes—as long as you’re aware of its illegitimacy.

Final Word

The Just Jump Mat is a part of strength & conditioning history—and still has a place in its present. Whether you upgrade to Plyomat or stick with Just Jump, the most important thing is understanding what your data really means, and how to use it to help athletes improve.

Test consistently and keep context at the core of your coaching.