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Article History

Received: 19 October 2017

Accepted: 13 February 2018

First Online: 20 February 2018

Ethics approval and consent to participate

: As this was a secondary analysis of de-identified existing data that had been collected for other research purposes, under Danish law these additional analyses did not require separate ethics approval. Ethics approval was granted for the original study ‘Backs on Funen’ (general population sample) from the Ethics Committee of Vejle and Funen Counties (approval # 20000042) and for the RCT (clinical sample) by the Ethics Committee for the Region of Southern Denmark (approval # S-VF-20060111). Participant consent was collected prior to study involvement in the original studies and renewed participant consent was not necessary as this study involved the use of a previously-published de-identified database according to the Danish Data Protection Agency.

: Not applicable

: Per Kjaer is a member of the Editorial Board of BMC Musculoskeletal Disorders. The other authors declare that they have no competing interests.

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