Enter the Jump Height and Contact Time into the calculator to determine the Reactive Strength Index. This calculator can also evaluate any of the variables given the others are known.

Reactive Strength Index Formula

Y = (2 * (L + W) + E) / 36

The following formula is used to calculate the Reactive Strength Index (RSI).

RSI = JH / CT

Variables:

  • RSI is the Reactive Strength Index
  • JH is the Jump Height (meters)
  • CT is the Contact Time (seconds)

To calculate the Reactive Strength Index, divide the Jump Height by the Contact Time. The result is the Reactive Strength Index, which measures an athlete’s explosive leg power.

What is a Reactive Strength Index?

The Reactive Strength Index (RSI) is a measurement used in sports science to evaluate an athlete’s explosive leg power, specifically their ability to change quickly from an eccentric to a concentric contraction. It is calculated by dividing the height jumped by the time spent on the ground during a depth jump or drop jump. A higher RSI indicates a greater level of reactive strength and plyometric ability, which is crucial in many sports for actions such as sprinting and jumping.

How to Calculate Reactive Strength Index?

The following steps outline how to calculate the Reactive Strength Index (RSI).

  1. First, determine the Jump Height (JH) in meters.
  2. Next, determine the Contact Time (CT) in seconds.
  3. Next, gather the formula from above = RSI = JH / CT.
  4. Finally, calculate the Reactive Strength Index (RSI).
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

Jump Height (JH) = 1.5 meters

Contact Time (CT) = 0.2 seconds