A New Measure of Reactivity

The Dynamic Rebound Index (DRI) was created to address a key limitation of the Reactive Strength Index (RSI).

RSI is calculated as jump height divided by ground contact time. As a result, it is heavily influenced by contact time. Short, stiff, low-displacement rebounds can score very well, even when the athlete produces minimal meaningful movement. In practice, RSI tends to reward quickness, not necessarily effectiveness.

Instead of focusing on jump height alone, DRI accounts for total vertical displacement (drop height plus jump height) relative to the time available to reverse momentum under gravity. This scales reactivity to the actual mechanical demand of the task, not just how fast the athlete leaves the ground.

Calculate and Share Your DRI and RSI

DRI vs RSI

The difference is not just the calculation. It's how the DRI behaves:

• Stiff, low-displacement strategies no longer dominate the score
• DRI increases only when short contact times are paired with meaningful displacement
• The metric aligns more closely with real stretch–shortening cycle demands seen in sport

In short, DRI provides a more complete picture of effective athletic reactivity.

More Resources on the Dynamic Rebound Index

1. Read our blog post, Dynamic Rebound Index: A New Mechanical Measure of SSC Performance
2. To really understand the measure and the math, check out the full publication from Lance Brooks.

I hope this helps,

Ramsey