RSI Test (run assessment, ~22 min)

What this assessment is

The RSI Test is the seeded run assessment that produces your Reactive Strength Index (RSI) from a drop-jump from a box. RSI is a leg-stiffness proxy used in run economy and injury risk monitoring.

Domain: run. Estimated duration: 22 minutes. Linked calculator: rsi.

Drop-jump only

Grepiac's RSI test and calculator support drop-jump RSI from a box exclusively. The continuous-hop / repeated-hop ("pogo") RSI variant, where the athlete bounces on the ground repeatedly, is a valid alternative protocol in the broader literature but is not supported by this calculator or assessment. The calculator's inputs assume one drop, one ground contact, one rebound. Do not try to log ground-hop data here; the formula will return a meaningless number.

Pogos and ground hops still have a role: as a training modality for improving RSI. They just are not the measurement protocol Grepiac uses.

The 3-step protocol (as seeded)

Warm-up (15 min): jog 10 minutes, then 10 bodyweight squats, 10 ankle bounces, 3 practice drop jumps at low height.
Drop jumps (5 min): step off (do not jump down) a 30 cm box. On ground contact, immediately rebound as high as possible. Minimise ground contact time. Perform 3 reps with 60 s rest between.
Record data: ground contact time and flight time for each rep from a contact mat, force plate, or slow-motion video.

The "step off" detail matters: jumping down adds vertical velocity that biases the drop height and skews RSI upward. Always step off.

Inputs the calculator asks for

Per rep, from the contact mat or video timing:

Ground Contact Time (seconds, typical range 0.08 to 0.25 s for clean drop jumps; the calculator flags anything outside ~0.06 to 0.40 s as unusual).
Flight Time (seconds).

How the calculator computes RSI

Two-step calculation (per the calculator source):

Jump height from flight time: h = g * t_flight^2 / 8, where g = 9.80665 m/s^2. This assumes take-off and landing happen at the same height, which is true for the drop-jump-from-box protocol when you step off and land on the same surface.
RSI: RSI = h / t_contact. Units: metres of jump height per second of ground contact.

Grepiac's outputs include both the computed RSI and the derived jump height, so a coach can sanity-check the inputs.

What the result tells you

High RSI (above ~2.5 m/s for most well-trained athletes): good leg stiffness, efficient stretch-shortening cycle.
Moderate RSI (1.5 to 2.5): typical of trained endurance athletes.
Low RSI (below 1.5): room for plyometric work, or signals fatigue / overtraining if it dropped from a higher baseline.

Use the athlete's own trend over time as the primary signal; cross-athlete comparison is less informative.

Equipment required

30 cm box or any stable platform of that height. The calculator's notes accept 20 to 40 cm; pick one box height and use it consistently across retests.
Contact mat or force plate for millisecond timing.
High-speed phone video with a frame-counter app is a passable fallback (240+ fps recommended).

When to retest

Every 6 to 12 weeks as a routine monitor.
Within a week of a heavy plyometric or strength block to catch fatigue.
Before a key race to confirm the athlete is fresh.

What ground-hop RSI is (and why we don't measure it here)

For reference: the continuous-hop variant measures RSI during a sustained sequence of small vertical hops on the ground (typically 10 to 15 hops, two-footed, hands on hips). It uses the same h / t_contact calculation per hop but averages over the sequence and has a slightly different calibration. It is useful in sports-science contexts where a drop jump is impractical.

Grepiac's calculator does not accept multi-hop input data. If you have a sports-science setup that uses ground-hop RSI, log a CoachNote with the value and protocol; do not try to put the number into the drop-jump calculator.