This article has been accepted for publication in British Journal of Sports Medicine, 2020 following peer review, and the Version of Record can be accessed online at http://dx.doi.org/10.1136/bjsports-2020-101983. Reuse of this manuscript version (excluding any databases, tables, diagrams, photographs and other images or illustrative material included where a another copyright owner is identified) is permitted strictly pursuant to the terms of the Creative Commons Attribution-Non Commercial 4.0 International (CC-BY-NC 4.0)
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