Funding for this research was provided by:
Received: 12 April 2019
Accepted: 27 August 2019
First Online: 17 September 2019
Ethics approval and consent to participate
: According to the declaration of Helsinki, all participants were fully informed of the potential benefits and risks of the study, both orally and written, before signing an informed consent. For participants under 16 years, both the players and their parents gave their written informed consent. The participants were fully informed of their rights to withdraw from the study at any time without providing any reason. This study was approved by the Norwegian Centre for Research Data for the storage of personal data (Approval reference number: 59063 / 3). The study adheres to CONSORT guidelines.
: Not applicable
: The authors declare that they have no competing interests.