Article
Open Access
Expand
On uneven ground: embracing the challenges of inter-limb asymmetries and their assessment
1 Centre of Research, Education, Innovation, and Intervention in Sport (CIFI2D), Faculty of Sport, University of Porto, Porto 4200-450, Portugal
2 Department of Nursing and Health Sciences, University of Vermont, Burlington, VT 05405, USA
3 Sport and Physical Activity Studies Centre (CEEAF), University of Vic–Central University of Catalonia, Vic 08500, Spain
4 Sport, Exercise, and Human Movement (SEAHM), University of Vic–Central University of Catalonia, Vic 08500, Spain
5 Integrative Neuromuscular Sport Performance Lab, Faculty of Kinesiology, University of Calgary, Calgary AB T2N 1N4, Canada
6 SPORT Research Group (CTS-1024), CIBIS (Centro de Investigación para el Bienestar y la Inclusión Social) Research Center, University of Almería, Almería 04120, Spain
7 Faculty of Human Kinetics, University of Lisbon, Lisboa 1649-004, Portugal
8 London Sport Institute, Faculty of Science and Technology, Middlesex University, London NW4 4BT, UK
Abstract

Inter-limb asymmetry is often misunderstood in sports and healthcare, with natural differences seen as problems usually needing correction. Evidence linking inter-limb asymmetries to increased injury risk or reduced performance is weak, and asymmetries of 5–15% (or even higher) typically do not increase the likelihood of injury. Assessing inter-limb asymmetries is a complex matter. Practitioners should select tests aligned with sports demands and track changes over time, rather than relying on single time point data. Ongoing temporal assessments help distinguish meaningful trends from natural fluctuations. Measurement error should also be considered to ensure changes exceed the minimal detectable change and reflect genuine performance or shifts in injury risk. Intra-individual analysis is recommended over averages across groups, as they can obscure meaningful variations. Arbitrary thresholds for what may be considered “normal” asymmetries oversimplify a continuous variable, potentially leading to misleading conclusions. Focusing on ranges (e.g., confidence intervals) instead of point values (e.g., mean) provides a more nuanced view. In addition, interpreting raw limb data alongside asymmetry metrics is crucial, as similar asymmetry percentages may arise from different limb strength profiles. Tracking raw data ensures that interventions improve performance, even if asymmetries persist. We provide a framework to help guide practitioners’ decisions. Task specificity and context, temporal stability, measurement quality, and raw performance data are key pieces of the puzzle. Before implementing “asymmetry-correcting” programs, practitioners should answer key questions, for which we provide a user-friendly decision tree. Not all asymmetries are likely to yield meaningful benefits if corrected, and intervening in asymmetry should result from a carefully reasoned process that requires establishing relevance, ensuring measurement quality, gathering appropriate data, and considering practical implications.

Keywords

asymmetry; inter-limb; human performance; thresholds; temporal stability; raw changes

Preview