title: Countermovement-Jump-Phase Characteristics of Senior and Academy Rugby League Players.
abstract: OBJECTIVE
  Gross measures of countermovement-jump (CMJ) performance are commonly used to track maturational changes in neuromuscular function in rugby league (RL). The purpose of this study was to conduct both a gross and a more detailed temporal-phase analysis of the CMJ performances of senior and academy RL players, to provide greater insight into how neuromuscular function differs between these groups.
  
  
  METHODS
  Twenty senior and 14 academy (under-19) male RL players performed 3 maximal-effort CMJs on a force platform, with forward dynamics subsequently employed to allow gross performance measures and entire kinetic- and kinematic-time curves to be compared between groups.
  
  
  RESULTS
  Jump height (JH), reactive strength index modified, concentric displacement, and relative concentric impulse (C-IMP) were the only gross measures that were greater for senior players (d = 0.58-0.91) than for academy players. The relative force- and displacement-time curves were similar between groups, but the relative power- and velocity-time curves were greater (d = 0.59-0.97) for the senior players at 94-96% and 89-100% of the total movement time, respectively.
  
  
  CONCLUSIONS
  The CMJ distinguished between senior and academy RL players, with seniors demonstrating greater JH through applying a larger C-IMP and thus achieving greater velocity throughout the majority of the concentric phase and at takeoff. Therefore, academy RL players should train to improve triple (ie, ankle, knee, and hip) extension velocity during the CMJ to bring their JH scores in line with those attained by senior players.
authors.forename: John J
authors.initials: JJ
authors.lastname: McMahon
authors.forename: Shannon
authors.initials: S
authors.lastname: Murphy
authors.forename: Sophie J E
authors.initials: SJE
authors.lastname: Rej
authors.forename: Paul
authors.initials: P
authors.lastname: Comfort
mesh_terms: D000328:Adult; D056352:Athletes; D054874:Athletic Performance; D001696:Biomechanical Phenomena; D005538:Football / Q000502:physiology*; D006801:Humans; D008297:Male; D009068:Movement; D055815:Young Adult
keywords: force–time; maturation; neuromuscular function; power–time; temporal phase analysis