Countermovement Rebound Jump Test: Full CMRJ Testing Protocol

A team's top scorer posts 38 cm on the Monday post-match countermovement jump test, identical to his pre-season baseline. Nothing to flag. Ask him to land off that jump and immediately fire into a second one, no reset, no second dip, and his ground contact time stretches from roughly 210 ms to 340 ms before he's even airborne again. The concentric number told you nothing. The reload told you almost everything.

That reload is the countermovement rebound jump, shortened to CMRJ in most performance labs: a standard countermovement jump landed and rebounded straight into a second maximal jump with the least ground time the athlete can produce. Cormack, Newton, McGuigan, and Doyle (2008) built the reliability case for this exact sequence using a cohort of 21 team-sport athletes, and a companion study the same year tracked it across an Australian Rules Football match week to show it flags neuromuscular fatigue that a plain jump-height number quietly misses. This guide covers what the CMRJ actually measures, three equipment options at different price points, a step-by-step protocol, the metrics worth logging, and the mistakes that quietly wreck the data before you ever get to interpret it.

What the CMRJ Measures That a Standard CMJ Does Not

A standard CMJ asks for one stretch-shortening cycle: dip, reverse, extend, leave the ground. It is mostly a test of concentric force production with a single elastic contribution layered on top. The CMRJ asks for a second stretch-shortening cycle immediately after landing from the first jump, under far less preparation time and with whatever fatigue jump one already loaded into the tendons and nervous system. That second cycle is where reactive strength actually shows up, and it behaves differently from raw jumping ability. For a refresher on the base movement before layering on a rebound, see our countermovement jump guide.

Gathercole, Sporer, Stellingwerff, and Sleivert (2015) compared traditional CMJ variables against a set of more reactive-leaning variables in a small cohort of team-sport athletes (n=17) following an acute fatiguing training session. Jump height alone sometimes failed to shift by a meaningful amount even when athletes reported clear fatigue on subjective scales; the reactive-style variables, the ones the rebound phase of a CMRJ is built to capture, moved more consistently across the group. That gap is the practical argument for adding a rebound to your jump testing menu rather than treating CMJ height as the whole story.

Equipment Options: Force Plate, Contact Mat, or IMU

The CMRJ lives and dies on two timing measurements: flight time and ground contact time, both accurate to single-digit milliseconds. Three tools get you there at very different costs.

Force plates remain the reference standard because they output the full force-time curve, not just the two timing gates. But for a weekly monitoring protocol run on 20-plus athletes, a contact mat or an IMU is usually the more realistic tool, and validation studies against force plates generally place both within an acceptable margin for tracking trend. Pair it with our RSI drop jump protocol for a fuller reactive strength picture.

Step-by-Step CMRJ Testing Protocol

Preparation

1. Warm up for 8-10 minutes: light cardio, dynamic hip and ankle mobility, then 3 sub-maximal countermovement jumps to prime the pattern.
2. Standardize hand position at the hips for every trial. An unrestricted arm swing adds 8-10 cm of variance to jump height and makes contact time comparisons across sessions unreliable.
3. Mark a consistent takeoff zone on the mat or plate so the athlete lands and rebounds from the same spot each trial.

Data Collection

1. Athlete performs a maximal countermovement jump from standing, hands on hips.
2. On landing, with no pause and no visible reset of the knee angle, the athlete immediately drives into a second maximal jump.
3. Record flight time and jump height for both jumps, plus the ground contact time between them.
4. Rest 90 seconds, then repeat for a total of 3 trials.
5. Discard any trial where the athlete visibly pauses or re-dips between jumps; that trial has become two separate CMJs, not a CMRJ.

The table below shows three trials from one athlete, including a discarded trial that illustrates why a single rep is not enough to trust.

Average the two clean trials rather than all three. Averaging in a discarded trial understates reactive capacity and will show up later as a false fatigue flag.

Key Metrics and How to Calculate Them

Four numbers come out of a CMRJ trial, and each one answers a slightly different question.

Takeoff velocity is worth computing too, since it converts flight time into a number that is easier to compare against velocity-based training zones elsewhere in a program. With g = 9.81 m/s², a flight time of 0.50 s converts to a takeoff velocity of roughly 2.45 m/s (9.81 × 0.50 ÷ 2). A rebound jump with a noticeably lower takeoff velocity than the initial CMJ, even at a similar flight time on paper, usually means the athlete traded height for a slower, more cautious landing.

Interpreting Your Numbers by Training Level

These bands are starting reference points from field-testing experience with team-sport populations, not a fixed lookup table. An individual's own baseline matters more than where they land in a general band.

Cormack, Newton, and McGuigan (2008) tracked these variables across roughly 17 elite AFL players over a match week and found jump height had recovered to baseline by 2 days post-match, while the flight time to contact time ratio was still measurably suppressed at that point. That gap in recovery speed is the reason to keep the rebound phase in your testing rather than dropping it for a faster, jump-height-only protocol.

Common Mistakes That Wreck the Data

Allowing a Reset Between Jumps

Any visible pause or re-dip after landing turns the trial into two separate CMJs rather than one CMRJ. Cue athletes to think reload, not reset, and discard any trial where ground contact time balloons past roughly 400 ms in a trained athlete.

Inconsistent Arm Position

Free arm swing on one trial and hands-on-hips on the next makes session-to-session comparison meaningless. Pick one arm position and hold it for every athlete, every session, for the life of the program.

Trusting a Single Session's FT:CT Ratio

Cormack et al. (2008) reported the flight time to contact time ratio as noticeably less reliable session-to-session than jump height alone, with a coefficient of variation in the high single digits versus roughly 4-5% for jump height in the same cohort. A one-off dip of 5-8% is closer to test noise than a real fatigue signal; look for a 10%+ shift from an athlete's own rolling baseline before acting on it.

Testing Without Recording Context

A CMRJ number without a note on sleep, travel, or the prior day's training load is hard to interpret months later. Log the context alongside the number.

Using CMRJ for Weekly Fatigue Monitoring

The CMRJ earns its place in a program as a recurring monitoring tool, not a one-off test day. A simple weekly structure for a team-sport program looks like this.

Build at least four clean baseline sessions before treating any single number as a decision point. A four-session average smooths over day-to-day noise and becomes the baseline every future test should be judged against, not a population norms table.