Reactive Strength Index Normative Data (RSI)

Reactive strength index (RSI) normative data varies by sport, sex, and test type, but general benchmarks for a drop jump are: under 1.0 (low), 1.0–2.0 (moderate), 2.0–3.0 (good), and above 3.0 (excellent) for trained adult athletes. For the 5-hop test, typical scores are lower, often between 1.5 and 2.5. These numbers come from field testing in sports science; they are guidelines, not strict cutoffs.

Formula

The most common RSI formula is:

RSI = Jump Height (m) ÷ Contact Time (s)

Where:

• Jump Height – the vertical displacement of the body’s center of mass during the jump phase, measured in meters (m).
• Contact Time – the time from first ground contact to takeoff, measured in seconds (s).
• RSI – the reactive strength index, expressed in meters per second (m/s).

Some protocols use a unitless version by dividing by the acceleration due to gravity (9.81 m/s²), but the m/s version is more common in practice.

Worked Example

Using the default values from the calculator above:

1. Jump height = 0.40 m
2. Contact time = 0.20 s
3. RSI = 0.40 ÷ 0.20 = 2.00 m/s

So with a 40 cm jump and 200 ms contact time, the RSI is 2.00 m/s. This is considered a “good� score for a trained athlete.

How RSI Is Measured

RSI is typically measured using one of two protocols:

• Drop Jump (DJ): The athlete drops from a box (usually 20–40 cm) and immediately jumps as high as possible after landing. Contact time is the time on the ground before takeoff.
• 5-Hop Test: The athlete performs five consecutive forward hops, and RSI is calculated as the distance covered divided by the total contact time.

Measurement tools include force plates (gold standard), contact mats, and optical timing systems. For field use, a contact mat is common and provides both jump height (via flight time) and contact time.

Normative Data by Population

Published norms are limited, but here are typical ranges from sports science literature:

• Recreational adults (untrained): 0.8–1.5 m/s
• College athletes (various sports): 1.5–2.5 m/s
• Elite male sprinters/jumpers: 2.5–3.5 m/s
• Elite female athletes: 1.8–2.8 m/s
• Youth athletes (12–16 yrs): 1.0–2.0 m/s

These are approximate; actual values depend on the test protocol, box height, and the athlete’s sport. For example, basketball players often score higher than distance runners.

How to Choose the Right Test

Choose a test based on your goal:

• Assess reactive strength capacity: Use the drop jump with a 30 cm box.
• Monitor fatigue or training load: Use the 5-hop test because it’s quick and less technically demanding.
• Compare to team norms: Use the same test and box height as the reference data.

Always standardize the box height, instruction (“jump as high as possible, minimize ground contact�), and warm-up.

Common Mistakes and Misconceptions

• Using different formulas: Some use RSI = flight time ÷ contact time (unitless). That gives different numbers, so always note which formula you used.
• Ignoring box height: Higher drop heights tend to increase contact time and lower RSI. Don’t compare scores from different box heights.
• Measuring jump height incorrectly: Jump height from flight time assumes takeoff and landing are at the same height, which is true for a drop jump but not for a countermovement jump with a different landing position.
• Not accounting for arm swing: Arm swing can increase jump height; standardize whether arms are allowed.

Limitations of RSI

RSI is a simple ratio, but it has limitations:

• It doesn’t capture the quality of movement (e.g., knee valgus, excessive forward lean).
• It assumes a linear relationship between height and contact time, which may not hold for all athletes.
• It is highly task-specific; a high RSI on a drop jump doesn’t guarantee good performance in a sport-specific movement.
• Normative data are sparse and often from small samples, so treat them as rough guides.

Frequently Asked Questions

What is a good RSI for a 16-year-old soccer player?

For a 16-year-old, a drop jump RSI of 1.5–2.0 m/s is typical. Elite youth athletes might reach 2.5, but anything above 2.0 is above average for that age.

Can I measure RSI without a force plate?

Yes. A contact mat that measures flight time and contact time is sufficient. Jump height is calculated from flight time using the formula: height = (g × flight_time²) / 8. Many timing systems do this automatically.

What’s the difference between RSI and RSI-modified?

RSI-modified (RSImod) is used for countermovement jumps without a ground contact phase. It is calculated as jump height divided by time to takeoff (from movement start to takeoff). It reflects slower, more voluntary force production.

Should I use a 20 cm or 40 cm box for the drop jump?

For most athletes, a 30 cm box is a good standard. Higher boxes (40 cm) are for advanced athletes; lower boxes (20 cm) are for beginners or those with lower strength. Consistency is more important than the exact height.

How often should I test RSI?

Every 4–6 weeks is common for monitoring training adaptations. Testing more frequently (e.g., weekly) can be useful during intense training to detect fatigue, but be mindful of adding extra jumps to the training load.

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in t | Jump height (m) | m | 0.40 | 0
in t2 | Contact time (s) | s | 0.20 | 0
out rsi | Reactive Strength Index | m/s | t / t2 | 2
out ratio | RSI (unitless) | - | (t / t2) / 9.81 | 2