Tuesday, 18 Jun 2024

Reactive Strength Index (RSI)

The Reactive Strength Index (RSI) is a crucial measurement for athletes involved in sports that require dynamic jumping activities. It assesses the muscle-tendon stress and reactive jump capacity, providing valuable insights into an athlete’s performance. The RSI is calculated by dividing the jump height by the ground contact time.

Testing Reactive Strength

The incremental drop jump test is the most commonly used method to calculate the reactive strength. It involves drop jumps from various heights, starting from a 30cm box and progressively increasing to a 75cm box. Additionally, repeat hopping and jumping tasks can be used to measure RSI. A quick and simple alternative is the “rebound jump test,” which consists of a single double jump. Another test called the 10/5 RSI involves a countermovement jump followed by a series of 10 repeated, bilateral hops.

Calculating RSI

To calculate the RSI, you need to determine the ratio between the jump height and the ground contact time. The jump height time refers to the duration between the participant’s feet leaving the timing mat or force platform and when they make contact with it again. The formula to calculate the jump height in meters is as follows: jump height = 4.9 x (0.5 x Time)². On the other hand, the ground contact time is the period between the first foot contact with the force platform and when the participant’s feet leave the mat.

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If an athlete jumps 36cm with a contact time of 0.18 seconds, their RSI would be 200. Athletes can improve their RSI by increasing their jump height, reducing their ground contact time, or working on both components.

It is also possible to calculate RSI using flight time instead of jump height. This alternative calculation is equally valid, as it allows for a straightforward conversion of jump height from jump time. Jump time is often easier to obtain, making the RSI calculation more accessible.

For more information on the Reactive Strength Index, you can refer to the following reference:

  • Flanagan, E.P., Ebben, W.P., and Jensen, R.L. (2008). Reliability of the reactive strength index and time to stabilization during depth jumps. Journal of Strength and Conditioning Research. 22(5), pp.1677-1682.

Related Pages

  • Incremental Drop Jump: This test involves jumping after dropping from various heights, starting from a 30cm box and progressively increasing to a 75cm box.
  • Dynamic Strength Index: This index represents the ratio of ballistic peak force to isometric peak force.
  • Vertical Jump Tests
  • Force Plate Vertical Jump
  • Multichannel Computerized Strength Dynamometer
  • About Force Plates/Platforms
  • Other Strength/Power Tests

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