Volleyball Attack Jump Repeatability Test: Measuring Late-Set Jump Decrement

An outside hitter puts away her first six kills of a five-set match off the same clean, high contact point every time. By set four, tied at 20-20, she's still swinging just as hard, but two straight attacks catch the tape instead of clearing it. A rested approach-jump reach test the next morning would say she's fine, because that test only asks for one clean jump, fully recovered. It never asks what actually decided those two points: how much reach does she lose once she has to load and jump for the fortieth time in a match, back to back, with only a rally's worth of rest?

That's what an attack jump repeatability test answers: a fixed series of maximal approach jumps on a realistic rally-to-rally rest interval, scored by the percentage drop in reach from the opening jumps to the closing ones. This guide covers the equipment, a step-by-step 12-jump protocol, the decrement and fatigue-index formulas, benchmark ranges, and what a hitter's decrement curve says about how she'll hold up in a fourth or fifth set.

Why a Rested Approach Jump Doesn't Show Late-Set Fatigue

A standard approach jump reach test, whether it's a Vertec touch or a force-plate spike jump, shows what a hitter can produce once, fully rested, off a clean approach. It says nothing about her twenty-eighth swing of a set, or the rushed approach she finds two seconds after a scramble dig. An attack jump repeatability test forces that question by stacking maximal approach jumps on a fixed, short rest and measuring how far reach height falls, a read on repeated-jump tolerance rather than peak jumping ability.

Sheppard, Gabbett, Taylor, Dorman, Lebedew, and Borgeaud (2007) built the foundational version for elite men's volleyball, basing the design on time-motion analysis of national-team matches and scoring jump and approach-movement decrement across repeated efforts. The parameters proved highly reliable, with intraclass correlations of .93 to .95 and typical error of just 0.54% to 2.44% between trials, and the test separated national-team starters from development-squad players in a way a single rested jump could not. That's the core argument for testing repeatability at all: two hitters can share an identical single reach and still diverge sharply on how much of it survives a full match.

Equipment: Force Plate, Contact Mat, or IMU for Approach Jumps

A single approach jump forgives an approximate Vertec read. Twelve jumps on a fixed rest do not; manual timing error compounds across every rep and can manufacture a decrement that isn't real, or bury one that is.

A Vertec alone can't capture 12 jumps in sequence with usable precision. A contact mat at the takeoff spot, or an IMU on the waist, logs flight time and ground contact automatically and hands a coach the decrement number before the hitter finishes her cooldown.

Step-by-Step Protocol: The 12-Jump Attack Repeatability Test

Preparation

1. Warm up 10-12 minutes: light cardio, dynamic hip and ankle work, then 3-4 sub-maximal approach jumps at the test run-up distance.
2. Fix the approach: same steps, same starting mark, same takeoff spot every rep. A hitter who shortens or lengthens the run-up mid-test invalidates the comparison.
3. No ball, no set target on the swing; the arm action can stay simplified so leg fatigue isn't masked by a hitter protecting a live attack.

Data Collection

1. Perform 3 blocks of 4 maximal approach jumps. Within a block, rest exactly 8 seconds between jumps, matching a rally-to-serve interval. Between blocks, rest 25 seconds, matching a side-out or timeout-length break.
2. Record reach height and plant-to-takeoff ground contact time on all 12 reps.
3. Run this once per session; a second full attempt just layers residual fatigue on the first and won't produce a clean read.
4. If a hitter visibly shortens the approach or pauses beyond the fixed rest window, discard that rep rather than estimating a value for it.

One hitter's actual 12-jump trial, recorded on a contact mat during preseason testing:

Block 1 (reps 1-4) averages 56.5 cm; block 3 (reps 9-12) averages 48.5 cm, a drop of roughly 14%. Contact time climbs from 180 ms to 254 ms over the same reps. Height falling while ground contact lengthens is what confirms a real fatigue signal, not noise on one or two reps.

Calculating Decrement %, Fatigue Index, and Plant-to-Takeoff RSI

Three numbers come out of a 12-jump trial, each answering a different question.

In the sample trial, decrement % comes out to (56.5 − 48.5) ÷ 56.5 × 100 = 14.2%, while the fatigue index using reps 1-3 versus 10-12 reads (57 − 48) ÷ 57 × 100 = 15.8%. RSI on rep 1 is 0.58 ÷ 0.180 = 3.22, and on rep 12 it's 0.47 ÷ 0.254 = 1.85, a 42.5% drop, roughly three times steeper than the height decrement. Contact time degrades on top of reach height, not instead of it, so a hitter whose reach decrement looks moderate but whose RSI decrement looks severe is staying on the floor longer to produce a comparable jump, worth flagging even when reach height alone looks acceptable.

Decrement Benchmarks by Training Level

These bands come from field testing with volleyball attackers, not a published norms table, so treat them as a starting reference. An athlete's own baseline matters more than the band she falls into.

Position matters here more than in most jump tests. Outside hitters and opposites, who take the bulk of a team's attacks, tend toward the better end of their range even with an unremarkable reach height, since match volume forces the quality to develop. Liberos, who rarely attack, often post a strong reach but a mediocre decrement, simply because the quality was never trained.

What the Decrement Curve Predicts About Late-Set Attacking

The decrement curve maps onto match moments more directly than a single reach-height number ever could. A hitter who drops sharply after jump 5-6 in testing is often the same hitter whose kill percentage falls off once a set's rally count climbs past 20. A hitter whose curve stays close to flat through block 3 is better positioned to keep finishing at the same contact point deep into a tied fourth or fifth set.

Gathercole, Sporer, Stellingwerff, and Sleivert (2015) tested a related idea in 11 male college-level team-sport athletes across six countermovement-jump trials around a fatiguing intermittent-exercise protocol. Their central finding: raw jump height alone was not the most sensitive marker of accumulated neuromuscular fatigue, while the flight-time-to-contraction-time ratio picked up fatigue changes that height missed, with effect sizes across the variable set ranging from trivial to moderate. The limitation is real, a small sample (n=11), non-volleyball athletes, and a running-based rather than jump-specific protocol, so exact figures don't transfer directly. What does transfer is the point this test is built on: height alone underreports fatigue, and a contact-time metric alongside it catches what height misses.

Mistakes That Distort the Decrement Number

Letting Hitters Pace the First Block

A hitter who knows 12 jumps are coming will sometimes hold back on jumps 1-4, flattening the true decrement. State before jump 1 that every rep is maximal; a shorter approach or lower arm swing on the early reps is the usual tell.

Varying the Approach Between Reps

A three-step and a four-step approach produce different reach heights and contact-time profiles. Lock the approach in during warm-up and don't let it drift across the 12 reps.

Changing the Rest Interval Session to Session

An 8-second within-block rest isn't comparable to a 12-second one; a longer gap lets more phosphocreatine resynthesis happen and understates real fatigue. Pick an interval and hold it constant.

Treating One Session's Number as Fixed

Decrement-style metrics carry more session-to-session variability than a single jump height. Build at least 3 baseline sessions before treating any single number as a decision point, and watch contact-time drift so a mild height decrement doesn't hide a steeper mechanical one.

Building It Into a Season Testing Calendar

This test fatigues athletes on purpose, so it doesn't belong in the same weekly rotation as a single reach test.

For the programming side, pair it with our volleyball jump training guide and vertical leap guide; this test is the measurement half of what those build toward.