Reactive Strength Index (RSI): Benchmarks, Testing and Programming

Reactive strength index answers a question jump height cannot. Not how high can you jump, but how much height do you get for every millisecond your foot spends on the ground. That ratio is what separates a fast, springy athlete from a strong one who needs time to express force.

It is also one of the easiest metrics to test badly. This guide covers what RSI measures, how to run a protocol you can trust, what the numbers mean, and how to programme for it.

What RSI actually measures

RSI is jump height divided by ground contact time. In a drop jump, the athlete steps off a box, lands, and immediately jumps again. The plate or mat records how long the foot was in contact and how high the athlete got.

A height of 30cm with 200ms of contact gives an RSI of 1.5. A height of 30cm with 300ms gives 1.0. Same height, different quality. The first athlete is producing force quickly, the second is absorbing and pushing over a longer window.

This is why RSI is sometimes called a reactivity measure. It is not a pure strength test and not a pure power test. It reflects the interaction between the stretch shortening cycle, tendon stiffness, and the athlete's ability to coordinate a fast transition from absorption to propulsion.

Testing protocol

A reliable protocol matters more than the specific box height. What matters is that you do the same thing every time.

The standard drop jump protocol

1. Athlete stands on a box, hands on hips.
2. They step off, not jump off, so there is no upward momentum at take off.
3. They land on both feet and jump as high and as quickly as possible.
4. They land back on the plates and hold the landing.
5. Three to five attempts, with 30 to 60 seconds between them, recording the best valid trial and the average.

Instruction wording changes the result. Telling an athlete to jump as high as possible produces a different trace to telling them to get off the ground as fast as possible. Pick one cue, write it down, and use it every time. Most programmes use a combined cue, land and jump as fast as you can, while trying to jump high.

Box height. 30cm is the most common default because it produces a fast contact without excessive landing forces for most athletes. Taller athletes and heavier athletes often produce a better score from 40cm. Testing two or three heights once will identify each athlete's sweet spot, defined as the height where contact time stays short while jump height remains high. Do not change height mid season for convenience.

Contact time thresholds. Contact times above roughly 250ms start to blend into a countermovement jump strategy rather than a reactive one. If contact time is consistently long, the score is telling you about absorption quality, not reactivity, and you should read it that way.

Benchmarks

Treat any benchmark table as a starting reference, not a verdict. Protocol differences, box height, device, and instruction all shift scores by more than the gap between adjacent bands.

| Population | Typical RSI (30cm drop jump) | | --- | --- | | Recreationally active adults | 1.0 to 1.5 | | Trained team sport athletes | 1.5 to 2.0 | | Highly trained jumpers and sprinters | 2.0 to 2.5 | | Elite reactive athletes | Above 2.5 |

The more useful comparison is the athlete against themselves. A five to ten percent shift in an athlete's own RSI, maintained across two or more tests, is a meaningful signal. A single session fluctuation is usually noise.

What RSI tells you about injury risk

Higher RSI is generally associated with better reactive qualities and, in several studies of field sport athletes, with lower injury incidence. The relationship is not a straight line. Very high RSI can coexist with very stiff, low compliance landing strategies, and those athletes may absorb load through bone and joint rather than muscle.

Practically, use RSI as one input among several. An athlete whose RSI is high but whose landing forces are extreme and whose ankle and knee control is poor does not need more plyometrics. They need landing mechanics and eccentric strength work first.

Programming to improve RSI

RSI improves through quality contacts, not volume. The training goal is to reduce ground contact time while maintaining output, which means low rep counts, full recovery, and high intent.

The progression that works

1. Landing mechanics. Teach absorption first with snap downs and landing holds. Low intensity, high attention.
2. Pogo and ankle stiffness work. Small amplitude, short contact, high frequency. Builds the ankle and foot contribution.
3. Low drop jumps. 20 to 30cm, low reps, focus on short contact. Quality over quantity.
4. Higher intensity plyometrics. Bounds, depth jumps, single leg variants, introduced once contact times are short and landing is controlled.
5. Sport specific reactivity. Reactive agility, sprint starts, and drill work that asks for the same quality in a chaotic environment.

Weekly contact volume

Track foot contacts, not sessions. For in season team sport athletes, a common working range is roughly 80 to 120 high quality contacts in a plyometric session, with total weekly contacts managed against the demands of competition. Off season and pre season can carry more. The number matters less than the intent behind each contact and the athlete's ability to repeat it.

Where RSI fits in the week

Test early in the week, after the lightest training day, so you are measuring readiness rather than accumulated fatigue. Place plyometric work early in a session while the nervous system is fresh, and never after heavy conditioning.

Common testing errors

• Letting the athlete jump off the box instead of stepping off. This adds upward momentum and inflates the score.
• Changing the cue between tests. Intent changes the trace more than most people expect.
• Using the best trial only. Report the average and the best, and note which you use for decisions.
• Testing on different surfaces. A sprung gym floor and a concrete weight room produce different contact times.
• Comparing across devices. Jump mats, phone apps, and force plates do not give interchangeable numbers.
• Testing after a heavy lower body session. You will measure fatigue, not reactivity.

Tracking it properly

RSI is most useful as a trend with context. That means the score, the protocol used, the athlete's recent training load, and their wellness responses should sit together. In Prospect, assessment results from VALD and other testing systems land on the athlete profile alongside programme completion and medical status, so a drop in RSI can be read against the week that produced it.

The habit to build is simple. Test the same way, at the same point in the week, and review the trend rather than the trial. Then let one metric drive one decision, whether that is reducing contacts, adding a landing focus, or leaving the athlete alone.

The short version

RSI is jump height per millisecond of ground contact, and it measures reactivity rather than raw power. Use a consistent drop jump protocol, understand that contact times above roughly 250ms change what you are measuring, and compare athletes to their own history. Improve it with low volume, high intent contacts and a landing first progression. Above all, let the number inform a decision rather than replace one.