A drop jump looks simple. An athlete steps off a box, lands, then rebounds as high as possible while keeping ground contact brief.

That short movement shows how quickly the body absorbs and returns force. It can also reveal how well the knees, hips, and ankles handle the landing.

Attention, pressure, and fatigue may affect execution, so coaches should control these factors when comparing results. Here is how to run the test, choose useful measures, and interpret the numbers without overreaching.

What the drop jump measures

A standard drop jump asks the athlete to minimise ground contact while achieving a high rebound. The instruction targets rapid force absorption and return rather than a slow, deep squat.

Three measures provide most of the useful information:

• Ground contact time: How long the feet remain on the ground between landing and take-off.
• Jump height: How high the athlete rises during the rebound.
• Reactive Strength Index (RSI): Jump height divided by ground contact time.

RSI is commonly measured with a force plate or contact mat. If flight time is measured in seconds, jump height in metres can be estimated as 4.9 × (0.5 × flight time)². That height is then divided by contact time to calculate RSI.

There is no single correct RSI value for every athlete. Results vary with box height, footwear, surface, instructions, and equipment. RSI is most useful when an athlete is tested repeatedly under the same conditions.

Read power alongside landing quality

Two athletes can record similar RSI values while using very different landing strategies.

Watch for inward knee movement, limited hip or knee flexion, and clear differences between the left and right sides. These patterns can affect whether a landing is controlled and repeatable.

Structured visual screens, such as the LESS-RT jump landing screen, can improve consistency between observers. However, live observation is best for large front and side cues. Small or rapid movements outside those views are harder to judge accurately.

This limitation is not unique to sport. Reviews of performance-based assessment in other fields reach a similar conclusion, that observing someone complete a real task reveals integrated function a laboratory measure misses, while remaining an imperfect instrument that works best alongside other data rather than instead of it.

How mental factors affect the movement

Studies that add a mental task to landing movements have reported stiffer landings, greater inward knee angles, and higher vertical forces. Distraction is therefore not just a mental issue, and the wider research on cognitive load in sport shows why it surfaces in an athlete’s mechanics rather than only in their decision-making.

If testing is intended to measure physical capacity, limit unnecessary distractions. If the goal is to examine performance under pressure, add the mental task deliberately and record it as part of the protocol.

How to run the test consistently

1. Complete a thorough warm-up that includes several submaximal hops.
2. Choose a suitable box height. Many protocols use 30cm, but use a lower box if the athlete cannot land and rebound with control.
3. Keep the hands on the hips to remove the effect of arm swing.
4. Step off the box instead of jumping upward or outward from it.
5. Cue brief ground contact and a high rebound.
6. Allow two practice repetitions, then record three trials.
7. Keep footwear, surface, box height, and rest intervals constant.

Use the same instructions word for word. If the wording changes between sessions, the athlete’s attentional focus may change with it, making the results harder to compare.

Measuring the test objectively

• Force plates and contact mats measure timing and support RSI calculations.
• Two-dimensional video captures basic front and side landing cues at relatively low cost.
• Marker-based three-dimensional capture provides detailed laboratory measurements of joint movement.
• Markerless three-dimensional capture estimates joint angles without attaching markers to the athlete, which can simplify preparation in busy testing spaces.

For a closer look at capturing landing mechanics and RSI with markerless kinematics, the drop jump test guide from Theia3D explains the main workflow.

Reading results without overreach

Compare each athlete with their own previous results instead of relying on squad rankings. A change is easier to interpret when the protocol and testing conditions remain stable.

Pair timing measures with landing notes or movement data. An RSI that stays steady while knee valgus, or inward knee motion, increases may still indicate a meaningful change.

This is where sport psychology becomes a testable variable. Attention and cognitive demand can be logged alongside output from a mat, force plate, or markerless system such as Theia3D.

FAQ

• What is RSI in simple terms? RSI compares how high an athlete rebounds with how long the feet remain on the ground. A higher ratio means the athlete produced more height relative to the time spent absorbing and returning force.
• Does pressure always hurt performance? No. Cognitive load can affect landing forces and joint positions, but responses vary by athlete and task. Test the effect under controlled conditions rather than assuming the result.
• How many trials should I record? Two practice repetitions followed by three recorded trials is a practical approach. Consistent instructions, recovery time, and testing conditions matter more than recording a large number of jumps.
• Can markerless capture replace a force plate? The tools answer different questions. Force plates and mats measure timing, while markerless systems estimate joint movement from video. They can complement each other, but neither should be treated as a direct replacement for the other.

Jeffrey Grant, a psychology graduate from the University of Hertfordshire, has a keen interest in the fields of mental health, wellness, and lifestyle.