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Test protocol · Reactive strength

Drop Jumpdrop · rebound · land

1Record2Upload3See the results
Why it matters: the drop jump tests how quickly the legs absorb a landing and turn it into a jump, the fast stretch-shortening cycle used in sprinting, cutting and jumping (Flanagan & Comyns, 2008). The landing also shows knee control. A jump mat gives you a contact time.VueMotion also shows how the athlete absorbed the drop and how they landed, from the side and the front.

The athlete stands on a box, steps off onto the drop marker, and in one motion absorbs the landing and jumps as high and as fast as possible, then sticks the landing and holds still. Three iPhones in portrait, synced with Controller-Capture, record the jump from both sides and the front.

RSI
reactive strength index
2
synced iPhones, portrait
5 m
camera distance
PhaseSet
Why it matters

A contact mat tells you how fast. VueMotion shows how.

Every drop jump gives you three layers that turn one jump into decisions for performance, injury risk, return to play, benchmarking and scouting.

RSI
Reactive strength

Reactive strength index, ground contact time and rebound jump height.

BPI
Rebound timing

Braking and propulsive phase times and the braking-propulsive index: how the contact is split.

LND
Landing control

Knee flexion, knee valgus and trunk position at contact and at the final landing.

01

Performance monitoring

Is reactive strength improving?

  • RSI Reactive strength index vs baseline and cohort.
  • Contact time Shorter contacts with the same rebound height mean a stiffer, faster leg.
  • Trend Track across a plyometric block.
02

Performance improvement

Is the athlete strength- or speed-limited?

  • Timing Long braking phases point to poor eccentric control; long propulsive phases to low power.
  • Two athletes, same impulse Equal jump impulse can come from high force in short time or low force over long time; look at contact time too.
  • Drop height Increase drop height only while RSI holds.
03

Injury risk reduction

Who lands in a way that loads the knee?

  • Knee valgus Greater knee valgus during a drop vertical jump predicted ACL injury in young female athletes (Hewett et al., 2005).
  • Stiff landing Little knee flexion at landing was linked to higher ACL injury risk (Leppänen et al., 2017).
  • Left vs right Side-to-side differences from the two side cameras.
04

Safer, faster return to play

Can the leg tolerate fast, high loads again?

  • Progression Start from a low box and progress height as RSI and landing quality allow.
  • Baseline Compare with pre-injury RSI and landing angles.
  • Quality first Clear landing mechanics before chasing contact time.
05

Benchmarking

How does the athlete compare?

  • Normative range RSI, contact time and jump height against sport and cohort, at the same drop height.
  • Profile Fast-short vs slow-long contact strategies across the squad.
  • Squad view Set standards by position.
06

Scouting & talent ID

Who has elastic, reactive legs?

  • Objective Calibrated RSI from video, comparable across venues.
  • Reactive talent High RSI marks athletes who use the stretch-shortening cycle well.
  • Landing Spot poor landing control early.

These metrics describe movement patterns linked to performance and injury risk in research. They support coaching and clinical judgement; they do not diagnose or predict an individual injury.

01 · Setup

Box, drop marker and three cameras

Place a box (the deck uses a 60 cm cube; enter the actual drop height as a tag) on a firm, flat surface with a firm landing area in front. Mark a small cross 20 cm out from the centre of the box: the drop marker. All two cameras are 3 m from this marker.

PhaseSet
Drop markerSide camerasFront camera
C1

Sagittal (left/right)

2 m from the drop marker on the athlete's left side, tripod, portrait, 1× lens.

C2

Frontal

2 m in front of the drop marker, facing the athlete, portrait. Both knees and feet clearly visible.

Capture in HD at 60 or 120 fps on iPhone (or 4K 120 fps on GoPro), Auto-FPS off, iPhone 11 or newer.

02 · Capture

Record in a few minutes

1

Equipment

3 iPhones (11 or newer), tripods, a stable box, tape for the drop marker and a measuring tape.

2

Box & marker

Box on a firm surface; mark a cross 20 cm out from the centre of the box.

3

Cameras

Three tripods 5 m from the marker: left side, right side and front, all portrait.

4

Tag + record

Choose the athlete, the Drop Jump tag and the drop height, then record with Controller-Capture.

5

Upload

Upload the original files and submit the AI request.

Athlete

  • Warm up, then a few practice drops from a low box
  • Hands on hips for every jump
  • Step off the box (don't jump off) onto the marker
  • Minimise contact time and jump as high as possible, then stick the landing and hold still

Camera settings

  • HD at 60 or 120 fps on iPhone (or 4K 120 fps on GoPro)
  • Auto-FPS off (Settings → Camera → Record Video)
  • Fixed tripod, 1× lens, no zoom or panning
  • Do Not Disturb on, Auto-Lock never

Scene & upload tips

  • Start recording before the athlete moves; stop after they are still again
  • No one else in any camera's view
  • Clothing that shows the knees helps the front view
  • Upload original files from the app; avoid AirDrop or messaging apps
03 · Outputs

What you get after upload

Reactive strength

Reactive strength index, ground contact time and rebound jump height.

Rebound timing

Braking phase time, propulsive phase time and braking-propulsive index.

Landing

Knee flexion, knee valgus and trunk position at contact and final landing.

Left vs right

Side-to-side comparison from the two side cameras.

AR video

Pose overlay for each camera.

Progress & norms

Every metric vs previous tests and norms at the same drop height.

Training tips

Plyometric progressions by level, from pogo jumps to multiple-response box jumps.

Linking reactive strength and landing to performance and injury

Metric Link to performance or injury Evidence

Performance linked to performance   Prospective linked to future injury in a cohort study   Mechanistic linked to tissue loading in lab studies   Practice coaching rationale

Metric definitions

Reactive strength
Reactive strength index (RSI)
Rebound jump height ÷ ground contact time. Higher = more height from a shorter contact.
Ground contact time (s)
Landing from the drop → take-off into the rebound.
Rebound jump height (m)
Height of the jump after the drop, from flight time.
Rebound timing
Braking phase time (s)
Contact → lowest point (absorbing the landing).
Propulsive phase time (s)
Lowest point → take-off.
Braking-propulsive index (BPI)
Braking phase time ÷ propulsive phase time.
Landing
Knee flexion (°)
Knee bend at contact and at the deepest point of the final landing (side).
Knee valgus (°)
Inward knee movement relative to hip and ankle (front).
Trunk position (°)
Forward and sideways lean of the trunk.
04 · Practitioner value

Reactive strength and landing in one jump

No contact mat

Three iPhones replace a mat for contact time and RSI, and add joint angles.

Strategy, not just output

Braking and propulsive phases show how the contact is used.

Landing screen built in

Both side views and the front view in every jump.

Training guidance

Results link to level-based plyometric progressions.

Fits the battery

Pair with the CMJ: drop jump for fast SSC, CMJ for slow SSC.

Repeatable

Same box height and hands-on-hips every time.

05 · Support

FAQs

What box height should I use?

The setup uses a 60 cm box. Lower boxes suit younger or less-trained athletes. Always enter the height as a tag and keep it the same between tests.

Step off or jump off?

Step off, so the drop height stays the same.

Do I need both cameras?

The standard setup uses tw synced cameras: one side and the front.

Are CSV exports and APIs available?

CSV/Excel export for Enterprise and Academy users, and API access for Enterprise users.

  1. Flanagan EP, Comyns TM. The use of contact time and the reactive strength index to optimize fast stretch-shortening cycle training. Strength and Conditioning Journal. 2008;30(5):32–38.
  2. Markwick WJ, Bird SP, Tufano JJ, Seitz LB, Haff GG. The intraday reliability of the Reactive Strength Index calculated from a drop jump in professional men's basketball. International Journal of Sports Physiology and Performance. 2015;10(4):482–488.
  3. Bosco C, Luhtanen P, Komi PV. A simple method for measurement of mechanical power in jumping. European Journal of Applied Physiology. 1983;50(2):273–282.
  4. Hewett TE, Myer GD, Ford KR, et al. Biomechanical measures of neuromuscular control and valgus loading of the knee predict anterior cruciate ligament injury risk in female athletes: a prospective study. American Journal of Sports Medicine. 2005;33(4):492–501.
  5. Leppänen M, Pasanen K, Kujala UM, et al. Stiff landings are associated with increased ACL injury risk in young female basketball and floorball players. American Journal of Sports Medicine. 2017;45(2):386–393.
  6. Padua DA, Marshall SW, Boling MC, et al. The Landing Error Scoring System (LESS) is a valid and reliable clinical assessment tool of jump-landing biomechanics: the JUMP-ACL study. American Journal of Sports Medicine. 2009;37(10):1996–2002.