Drop Jump Test: protocol and how to calculate the RSI

The Drop Jump Test is the go-to plyometric test. Unlike a "normal" vertical jump, here the athlete drops from a preset height and must bounce back up as fast and as high as possible, which directly stresses the quality of the stretch-shortening cycle (SSC).

It's a highly informative test, but it's also demanding on the lower body structures, so it's best introduced once the athlete already has a solid base of strength and simpler jumps.

What does this test measure?

It assesses the reactive capacity of the lower body: how well and how quickly the neuromuscular system can absorb a fall and convert that energy into a vertical jump, minimizing ground contact time. It's the basis for calculating the Reactive Strength Index (RSI).

Equipment needed

• Box or platform of known height (usually 20-40 cm to start, adjustable by level)
• Contact mat, force plate, or jump mat to measure flight time and contact time
• Firm, flat landing surface

Test protocol

1. The subject stands on the box, feet close to the edge
2. Tell them to step off (not jump down) onto the floor, landing on both feet at once
3. The instant they make contact with the floor, they must rebound immediately upward with maximum effort, minimizing the time their feet spend on the ground
4. Hands stay on the hips to isolate leg work
5. The measurement system records flight time (to calculate jump height) and ground contact time
6. Perform 3 attempts at the same drop height and record the best (or most representative)
7. To build a fuller profile, repeat with different drop heights (20, 30, 40 cm) and check at which height the RSI is highest

Common mistakes

• Jumping down from the box instead of stepping off (this completely changes the nature of the stimulus)
• Using an excessive drop height for the athlete's level, increasing contact time instead of improving the rebound
• Moving the arms during the jump, adding a coordination component that distorts the leg measurement
• Introducing this test without a prior base of lower-body strength, increasing overload risk

How to interpret the result

The key result is the Reactive Strength Index (RSI), calculated as jump height (m) divided by contact time (s):

RSI	Interpretation
< 1.0	Low reactive capacity — prioritize base strength work before advanced plyometrics
1.0 - 1.5	Moderate reactive capacity, typical of recreational athletes
1.5 - 2.5	Good reactive capacity, common in trained athletes
> 2.5	Very high reactive capacity, typical of elite athletes in jump/sprint disciplines

If you calculate RSI at several drop heights, the point where RSI peaks indicates the "optimal drop height" for that athlete at that point in time — a very useful data point for programming plyometrics.

Relationship with other tests

The Drop Jump is the central piece for calculating RSI, but it's worth contextualizing it with other jump tests that don't involve such a pronounced stretch-shortening cycle:

• Reactive Strength Index (RSI) — a deeper dive into this concept and how to use it in programming
• CMJ (Countermovement Jump) Test — comparing the Drop Jump with the CMJ helps clarify whether the "problem" is concentric strength or reactive capacity

Unlike the CMJ (which starts from standing, with a countermovement controlled by the athlete) or the Squat Jump (no countermovement), the Drop Jump introduces a prior fall with impact velocity determined by the box height, making it much more specific to the SSC.

Track and monitor

The Drop Jump produces two data points (jump height and contact time) that, combined, give you the RSI: a metric very sensitive to fatigue and plyometric training quality. With Movalytics you can log both values at different drop heights and let the app calculate the RSI automatically, helping you decide when to progress the drop height or when to reduce plyometric load.

Frequently asked questions

What box height should I start with? 20-30 cm is a good starting point for most athletes. Only increase the height if RSI improves or holds steady; if it clearly worsens, that's a sign the height is too much for that stage. Is it the same as a Squat Jump or a CMJ? No. The Squat Jump and CMJ start from standing and measure concentric strength (with or without a countermovement). The Drop Jump introduces a prior fall and specifically measures the reactive capacity of the stretch-shortening cycle. Is it safe for any athlete? It's a demanding test for the lower-body tendons and joints. The athlete should already have experience with basic jumps (CMJ, Squat Jump) before introducing the Drop Jump.