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. 2018 Nov 1;10:18. doi: 10.1186/s13102-018-0107-3

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© The Author(s). 2018

Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

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Fig. 1 — PRISMA Flow Diagram: 485 studies between the years 1970 and 2017 were identified. Two hundred and eighty four studies were screened and 214 excluded after reviewing their abstracts. For the remaining 70 studies, examination of the full text manuscript was conducted but only 29 articles met the eligibility criteria