They accelerate with lightning speed, change direction in a flash, and every stride of their sprint seems light and almost effortless. As soon as they land after a jump theyвЂ™re perfectly balanced and firing off into the next movement. TheyвЂ™re basically a spring in human form. Now imagine an athlete with an incredibly high RSI. Not only is this athlete going to play worse, but theyвЂ™re exposing themselves to an increased injury risk every single time that they play. Every time they have to rapidly accelerate and sprint they just look soft, like theyвЂ™re losing power with every step. Every time they land after a jump it looks awkward and takes them ages to regain their balance and continue with the game. Imagine an athlete with an incredibly poor RSI. Why is reactive strength index important for sport? RSI in Action

Therefore a better RSI score suggests that an athlete is better able to absorb eccentric forces on landing, effectively utilise their stretch shorten cycle and then produce force concentrically. Similarly, if an athlete is able to land and jump again very quickly, then they will have a better RSI. So, if an athlete is able to jump really high after landing, then they will have a better RSI. It was first developed in 1995 by Young as part of the Strength Qualities Assessment Test (SQAT) in collaboration with the International Athletics Association. It is a ratio of how high an athlete jumps after landing, versus how long they were in contact with the ground. The reactive strength index (RSI) is a test designed to measure an athleteвЂ™s reactive jump capacity, specifically how well an athlete is able to cope with stresses applied through landing in jumping and plyometric activities. 13 Reference What is reactive strength index (RSI)?.9 Issues with the reactive strength index.8 Validity & Reliability of RSI testing.6 What is a good reactive strength index?.4 How do you calculate reactive strength index?.2 Why is reactive strength index important for sport?.1 What is reactive strength index (RSI)?.

Reactivity chart