Establishing the Noise: Interday Ecological Reliability of Countermovement Jump Variables in Professional Rugby Union Players. Issue 11 (5th November 2022) - Howarth, David J.
Abstract : Supplemental Digital Content is Available in the Text. Abstract: Howarth, DJ, Cohen, DD, McLean, BD, and Coutts, AJ. Establishing the noise: interday ecological reliability of countermovement jump variables in professional rugby union players. J Strength Cond Res 36(11): 3159–3166, 2022—The purpose of this study was to examine the interday "ecological" reliability of a wide range of ground reaction force–derived countermovement jump (CMJ) variables. Thirty-six male, professional rugby union players performed 3 CMJs on 4 separate days over an 8-day period during the first week of preseason. We calculated reliability for 86 CMJ variables across 5 interday combinations using 2 criteria: mean output across 3 jump trials (Mean3 ) and single output from the highest jump (BestJH ). Interday coefficient of variation (CV) of the 86 variables in each CMJ phase, for Mean3 and BestJH, respectively, ranged between concentric = 2–11% and 2–13%; eccentric = 1–45% and 1–107%; and landing = 4–32% and 6–45%. Mean3 interday CV was lower in all 86 variables across every interday combination, compared with BestJH . CVs were lower in our cohort than previous studies, particularly for eccentric phase variables. There was no meaningful difference between interday conditions, suggesting any 2-day combination conducted within the first 8 days of preseason, represents a measure of "noise." We did not apply arbitrary reliability "cut-offs" used in previous work (e.g., CV <10%); therefore, our analysis provides reference reliability for a wide range of CMJ variables. However, we recommend that practitioners assess reliability in their athletes, as it is likely to be environment, protocol, and cohort specific.