The calculation, thresholds and reporting of inter-limb strength asymmetry: a systematic review

Parkinson, A.O., Apps, C.L. ORCID: 0000-0002-7354-0003, Morris, J.G. ORCID: 0000-0001-6508-7897, Barnett, C.T. ORCID: 0000-0001-6898-9095 and Lewis, M.G.C. ORCID: 0000-0001-5918-3444, 2021. The calculation, thresholds and reporting of inter-limb strength asymmetry: a systematic review. Journal of Sports Science and Medicine, 20, pp. 594-617. ISSN 1303-2968

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The prevalence of inter-limb strength differences is well documented in the literature however, there are inconsistencies related to measurement and reporting, and the normative values and effects associated with inter-limb asymmetry. Therefore, the aims of this systematic review were to: 1) assess the appropriateness of existing indices for the calculation of asymmetry, 2) interrogate the evidence basis for literature reported thresholds used to define asymmetry and 3) summarise normative levels of inter-limb strength asymmetry and their effects on injury and performance. To conduct this systematic review, scientific databases (PubMed, Scopus, SPORTDiscus and Web of Science) were searched and a total of 3,594 articles were retrieved and assessed for eligibility and article quality. The robustness of each identified asymmetry index was assessed, and the evidence-basis of the identified asymmetry thresholds was appraised retrospectively using the references provided. Fifty-three articles were included in this review. Only four of the twelve identified indices were unaffected by the limitations associated with selecting a reference limb. Eighteen articles applied a threshold to original research to identify “abnormal” asymmetry, fifteen of which utilised a threshold between 10-15%, yet this threshold was not always supported by appropriate evidence. Asymmetry scores ranged between and within populations from approximate symmetry to asymmetries larger than 15%. When reporting the effects of strength asymmetries, increased injury risk and detriments to performance were often associated with larger asymmetry, however the evidence was inconsistent. Limitations of asymmetry indices should be recognised, particularly those that require selection of a reference limb. Failure to reference the origin of the evidence for an asymmetry threshold reinforces doubt over the use of arbitrary thresholds, such as 10-15%. Therefore, an individual approach to defining asymmetry may be necessary to refine robust calculation methods and to establish appropriate thresholds across various samples and methodologies that enable appropriate conclusions to be drawn.

Item Type: Journal article
Alternative Title: Inter-limb strength asymmetry
Publication Title: Journal of Sports Science and Medicine
Creators: Parkinson, A.O., Apps, C.L., Morris, J.G., Barnett, C.T. and Lewis, M.G.C.
Publisher: Journal of Sports Science and Medicine
Date: 10 August 2021
Volume: 20
ISSN: 1303-2968
Rights: ©Journal of Sports Science and Medicine (2021). This work is licensed under a Creative Commons License Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
Divisions: Schools > School of Science and Technology
Record created by: Linda Sullivan
Date Added: 17 Aug 2021 09:40
Last Modified: 17 Aug 2021 09:40

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