title: Biomechanical symmetry in elite rugby union players during dynamic tasks: an investigation using discrete and continuous data analysis techniques.
abstract: BACKGROUND
  While measures of asymmetry may provide a means of identifying individuals predisposed to injury, normative asymmetry values for challenging sport specific movements in elite athletes are currently lacking in the literature. In addition, previous studies have typically investigated symmetry using discrete point analyses alone. This study examined biomechanical symmetry in elite rugby union players using both discrete point and continuous data analysis techniques.
  
  
  METHODS
  Twenty elite injury free international rugby union players (mean ± SD: age 20.4 ± 1.0 years; height 1.86 ± 0.08 m; mass 98.4 ± 9.9 kg) underwent biomechanical assessment. A single leg drop landing, a single leg hurdle hop, and a running cut were analysed. Peak joint angles and moments were examined in the discrete point analysis while analysis of characterising phases (ACP) techniques were used to examine the continuous data. Dominant side was compared to non-dominant side using dependent t-tests for normally distributed data or Wilcoxon signed-rank test for non-normally distributed data. The significance level was set at α = 0.05.
  
  
  RESULTS
  The majority of variables were found to be symmetrical with a total of 57/60 variables displaying symmetry in the discrete point analysis and 55/60 in the ACP. The five variables that were found to be asymmetrical were hip abductor moment in the drop landing (p = 0.02), pelvis lift/drop in the drop landing (p = 0.04) and hurdle hop (p = 0.02), ankle internal rotation moment in the cut (p = 0.04) and ankle dorsiflexion angle also in the cut (p = 0.01). The ACP identified two additional asymmetries not identified in the discrete point analysis.
  
  
  CONCLUSIONS
  Elite injury free rugby union players tended to exhibit bi-lateral symmetry across a range of biomechanical variables in a drop landing, hurdle hop and cut. This study provides useful normative values for inter-limb symmetry in these movement tests. When examining symmetry it is recommended to incorporate continuous data analysis techniques rather than a discrete point analysis alone; a discrete point analysis was unable to detect two of the five asymmetries identified.
authors.affiliation: Sports Medicine Department, Sports Surgery Clinic, Santry Demesne, Dublin, Ireland ; School of Health and Human Performance, Dublin City University, Dublin, Ireland ; Insight Centre for Data Analytics, Dublin City University, Dublin, Ireland.
authors.forename: Brendan
authors.initials: B
authors.lastname: Marshall
authors.affiliation: Sports Medicine Department, Sports Surgery Clinic, Santry Demesne, Dublin, Ireland ; Centre for Health, Exercise and Sports Medicine, University of Melbourne, Melbourne, Australia.
authors.forename: Andrew
authors.initials: A
authors.lastname: Franklyn-Miller
authors.affiliation: School of Health and Human Performance, Dublin City University, Dublin, Ireland ; Insight Centre for Data Analytics, Dublin City University, Dublin, Ireland.
authors.forename: Kieran
authors.initials: K
authors.lastname: Moran
authors.affiliation: Sports Medicine Department, Sports Surgery Clinic, Santry Demesne, Dublin, Ireland.
authors.forename: Enda
authors.initials: E
authors.lastname: King
authors.affiliation: Sports Medicine Department, Sports Surgery Clinic, Santry Demesne, Dublin, Ireland ; School of Health and Human Performance, Dublin City University, Dublin, Ireland ; Insight Centre for Data Analytics, Dublin City University, Dublin, Ireland.
authors.forename: Chris
authors.initials: C
authors.lastname: Richter
authors.affiliation: Sports Medicine Department, Sports Surgery Clinic, Santry Demesne, Dublin, Ireland ; School of Health and Human Performance, Dublin City University, Dublin, Ireland ; Insight Centre for Data Analytics, Dublin City University, Dublin, Ireland.
authors.forename: Shane
authors.initials: S
authors.lastname: Gore
authors.affiliation: Department of Life Sciences, Roehampton University, London, UK.
authors.forename: Siobhán
authors.initials: S
authors.lastname: Strike
authors.affiliation: Sports Medicine Department, Sports Surgery Clinic, Santry Demesne, Dublin, Ireland ; Centre for Health, Exercise and Sports Medicine, University of Melbourne, Melbourne, Australia ; Department of Medicine, University College Cork, Cork, Ireland.
authors.forename: Éanna
authors.initials: É
authors.lastname: Falvey
keywords: Cutting; Dominant versus non-dominant; Kinematics; Kinetics; Landing