Jump metrics

Every rep produces a handful of numbers, all derived from Metric tracking your body through the entire jump. We surface the metrics that are reliable enough to train off, and skip the ones that look impressive but can’t be measured well without actual force data. Here’s what each one means and how Metric Jump works it out.

Jump height

The headline number, and the most reliable in jump testing. It’s how high your centre of mass rises from a standing start. Metric Jump derives it from your takeoff velocity, the same calculation as a force plate. Because it’s built on takeoff velocity rather than time in the air, you can’t inflate or cheat your jump height by tucking your legs on landing the way you can on a jump mat or with a flight-time app.

You’ll also see your height as a percentage of your personal best, so each rep can be easily compared to your own training context in real time.

Takeoff velocity

Sometimes called peak velocity. How fast your body is moving the instant you leave the ground, read straight from your centre-of-mass motion at takeoff. Velocity is a sensitive signal: it tracks improving performance, and it also reflects readiness and fatigue from day to day.

Tip: Track trends, not single reps. Day-to-day fluctuations are normal. The signal is in where your numbers move across weeks, or any large dips that might signal low readiness.

Reactive Strength Index (RSI)

How much height you produce relative to the time you spent producing it. RSI is your explosiveness number: two athletes can jump the same height, but the one who got there in less time is more reactive. Metric Jump uses a modified RSI calculation method, from your jump height and the time from the start of your countermovement to takeoff, so a quicker, snappier jump scores higher than a slow grind to the same height.

It’s one of the most trackable extras beyond height, which makes it a strong readiness and fatigue signal alongside takeoff velocity.

Impulse

The mechanical cause of the jump: the net force you applied multiplied by the time you applied it. Impulse is what actually launches you, and it’s the most reliable force-based number we can read from your jump without actual lab-grade force plates.

Flight time

How long you’re in the air, from takeoff to landing. Metric Jump reads it from your centre of mass rather than a contact mat, so a tucked or soft landing won’t inflate it the way it can on a jump mat.

Why no peak power or rate of force development? Calculating these from a phone camera gives a noisy signal that isn’t reliable enough to add real value. Rather than fake it, we leave them off instead of showing a number you can’t trust. Every metric we show is one we’d stand behind.

Comparing jumps in a set

When a set holds more than one jump type, Metric Jump compares them: eccentric utilisation ratio, left-right symmetry, arm swing contribution, and bilateral index. Those paired scores, and which jumps each one needs, live in Composite jump analytics.