Abstract
BackgroundWhile 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.MethodsTwenty 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.ResultsThe 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.ConclusionsElite 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.Electronic supplementary materialThe online version of this article (doi:10.1186/s13102-015-0006-9) contains supplementary material, which is available to authorized users.
Highlights
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
Discrete point findings for the drop landing, hurdle hop and cut are displayed in Tables 1, 2 and 3, respectively
The analysis of characterising phases (ACP) identified two additional asymmetries not identified in the discrete point analysis
Summary
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. Angle and moment variables at the ankle [9, 10], knee [7, 11], hip [8, 12], pelvis [13] and torso [14], as well as ground reaction forces [15] and ground contact times [16] have all been implicated in the development of lower extremity injury Such injuries include ankle ligament injury [10], tibial stress fracture [11], knee ligament injury [8] and patellofemoral pain syndrome [17]. It is suggested that a notable asymmetry in these biomechanical factors may increase the risk of lower extremity injury in one limb over the other [7, 6]
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