Patrice

The RJT+5cm rule: A simple heuristic for quick & easy drop-jump height optimization. A common approach is to use a DJ box/height height 🟰 CMJ jump height when starting DJ plyometric training. A more valid & accurate method is the Rebound Jump Test ➕ 5cm rule. Take the ave. jump height in 10-5 RJT & add 5cm to it. Short contact times, fast SSC focus means 10-5 RJT is more similar to demands of DJ - so why use CMJ data? Different joint actions, longer CTs, different SSC mechanism The 5cm addition accounts for phenomenon where many athletes "step down" off box rather than stepping out off box, especially in the early stages of DJ training. +5cm is a very rough estimation based on: 🔸@Lisacostley research showing inherent variability of "actual drop height" (ADH) 🔸Bobbert research showing ADH can be up to 10cm less than box height used 🔸5cm is the increment of box height available! My own experience: for box heights of 20-40cm, there can be diff of 4-7cm vs ADH and this can be as high as 8-10cm for box heights of 50-70cm. Let's walk it through: Combat sport athlete CMJ = 44cm 10-5 RJT = 2.7 RSI 10-5 RJT (height) = 51cm Using the traditional CMJ heuristic, we'd start their DJ training w/ 45cm box height. If we use the RJT + 5cm heuristic, our starting DJ box height would be 55cm. Let's look at this athlete's DJ reactive strength incremental profile (done 3-4 wks after CMJ & RJT data) The athlete hits their optimal RSI at 50-60cm. Had we used CMJ method, we might be utilizing a box height of 5-10cm lower than necessary. With the RJT+5cm method, we get a DJ box height of 56cm: right in ballpark of optimal profile [and no, it doesn't always work out as cleanly as this - but I do think the RJT+5 method is typically closer and logically more appropriate than CMJ approach]