Our aims were to assess single-leg balance in rugby union athletes and compare the stability indices between legs and between positions. Thirty athletes, forwards and backs (n = 15/15), performed single-leg balance measured at two difficulty levels (Level 8: more stable and Level 2: less stable) using the Biodex Balance SD System. The backs’ nonpreferred leg had worse scores in medial–lateral and overall indices (effect size = 1.05 and 0.63) compared with the preferred leg on Level 8 stability. Backs had better scores in all indices in the preferred (effect size = −1.20 to −1.82) and nonpreferred (effect size = −0.66 to −1.36) legs compared with the forwards at both stability difficulties. Asymmetry between the two legs is also present between forwards and backs when examined on an individual basis. This study illuminates the importance of single-leg balance screening among rugby athletes to detect individuals with asymmetries in balance that may increase the risk of lower-extremity injury.
Scott R. Brown, Matt Brughelli and Seth Lenetsky
Matt R. Cross, Farhan Tinwala, Seth Lenetsky, Scott R. Brown, Matt Brughelli, Jean-Benoit Morin and Pierre Samozino
The assessment of horizontal force during overground sprinting is increasingly prevalent in practice and research, stemming from advances in technology and access to simplified yet valid field methods. As researchers search out optimal means of targeting the development of horizontal force, there is considerable interest in the effectiveness of external resistance. Increasing attention in research provides more information surrounding the biomechanics of sprinting in general and insight into the potential methods of developing determinant capacities. However, there is a general lack of consensus on the assessment and computation of horizontal force under resistance, which has resulted in a confusing narrative surrounding the practical applicability of loading parameters for performance enhancement. As such, the aim of this commentary was twofold: to provide a clear narrative of the assessment and computation of horizontal force in resisted sprinting and to clarify and discuss the impact of methodological approaches to subsequent training implementation. Horizontal force computation during resisted sleds, a common sprint-training apparatus in the field, is used as a test case to illustrate the risks associated with substandard methodological practices and improperly accounting for the effects of friction. A practical and operational synthesis is provided to help guide researchers and practitioners in selecting appropriate resistance methods. Finally, an outline of future challenges is presented to aid the development of these approaches.