Footnotes

• Twitter Follow Mark Halstead at @stlsportsmed

• Contributors MEH, BEB and KM have all provided substantial contributions to the conception or design of the work, or the acquisition, analysis or interpretation of data; drafting the work or revising it critically for important intellectual content; provided final approval of the version published; and are in agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

• Competing interests None declared.

• Provenance and peer review Not commissioned; externally peer reviewed.