Funding for this research was provided by:
Fédération Internationale de Football Association
First Online: 18 January 2018
Compliance with Ethical Standards
: The authors gratefully acknowledge FIFA (Fédération Internationale de Football Association) for the funding of this review.
: Annika Prien, Alexander Grafe, Roland Rössler, Astrid Junge and Evert Verhagen declare that they have no conflicts of interest relevant to the content of this review.