- Correspondence to Professor Jan Ekstrand, Department of Medical and Health Sciences, Football Research Group, Linköping University, Solstigen 3, Linköping S-589 43, Sweden;
- Received December 15, 2012
- Revised April 6, 2013
- Accepted April 13, 2013
- First published May 5, 2013.
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.