Jump metrics — Docs

Every jump produces a handful of numbers. Metric tracks your body through the whole jump and derives each number from that motion. Metric Jump shows the metrics that are reliable enough to train off. It leaves out the ones that look impressive but need actual force data to measure well.

Jump height

Jump height is the headline number and the most reliable metric in jump testing. It is how high your centre of mass rises from a standing start. Metric Jump derives it from your takeoff velocity. This is the same calculation a force plate uses.

Jump height is built on takeoff velocity, not on time in the air. So you cannot inflate or cheat your jump height by tucking your legs on landing. On a jump mat or in a flight-time app, that tuck does raise the number.

Metric Jump also shows your height as a percentage of your personal best. You can then compare each rep to your own training context in real time.

Takeoff velocity

Takeoff velocity is sometimes called peak velocity. It is how fast your body moves the instant you leave the ground. Metric Jump reads it straight from your centre-of-mass motion at takeoff.

Velocity is a sensitive signal. It tracks improving performance. It also reflects your 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 in any large dip that may point to low readiness.

Reactive Strength Index (RSI)

RSI is how much height you produce relative to the time you spend producing it. RSI is your explosiveness number. Two athletes can jump the same height. The athlete who gets there in less time is more reactive.

Metric Jump uses a modified RSI calculation method. It works RSI out 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.

RSI is one of the most trackable extras beyond height. That makes it a strong readiness and fatigue signal alongside takeoff velocity.

Impulse

Impulse is the mechanical cause of the jump. It is the net force you applied multiplied by the time you applied it. Impulse is what launches you. It is the most reliable force-based number Metric can read from your jump without lab-grade force plates.

Flight time

Flight time is how long you are in the air, from takeoff to landing. Metric Jump reads it from your centre of mass, not from a contact mat. So a tucked or soft landing does not inflate it. On a jump mat, that landing can inflate the number.

Why Metric Jump leaves out peak power and rate of force development

Calculating peak power or rate of force development from a phone camera gives a noisy signal. That signal is not reliable enough to add real value. Metric leaves both metrics off rather than fake a number you cannot trust. Metric stands behind every metric it shows.

Comparing jumps in a set

When a set holds more than one jump type, Metric Jump compares them. The paired scores are eccentric utilisation ratio, left-right symmetry, arm swing contribution, and bilateral index. See Composite jump analytics for those scores and for the jumps each one needs.