The Reliability of Countermovement Jump Performance and the Reactive Strength Index in Identifying Drop-Jump Drop Height in Hurling Players

Abstract

The purpose of this study was to estimate the inter-day reliability of countermovement jump performance (CMJ) and the reactive strength index (RSI) in identifying drop-jump drop height in male hurling players. Eighteen male hurling players volunteered to participate. Subjects performed the CMJ and drop-jump test for RSI during the same sessions on three separate occasions a minimum of 48 hours apart. Subjects performed three CMJs and two drop-jumps from five different heights in an incremental manner (0.20, 0.30, 0.40, 0.50, 0.60 m). The results displayed acceptable levels of relative and absolute reliability for the following CMJ measures: height, velocity, force, power and average eccentric rate of force development measures (RFD). Absolute and relative peak concentric rate of force development from the CMJ test were found to have low levels of absolute reliability due to high CV% values. RSI and identified drop height from the drop-jump test displayed acceptable reliability (ICC single measure = 0.88 and 0.92 respectively; CV% = 6% and 10% respectively). Furthermore, limits of agreement random error displayed acceptable reliability for CMJ and drop-jump measures from estimated feasible minimum a priori sample sizes based upon limits of agreement. In conclusion, CMJ force-time measures (excluding peak concentric RFD measures), RSI and the identified drop height have acceptable absolute and relative reliability. For the sport science practitioner involved in hurling and for hurling players, this means that the CMJ test is reliable for kinetic and kinematic variables and the drop-jump test provides a means of developing a reactive strength profile and a means of individualizing drop height for drop-jump training.