Correspondence to Dr Karsten Hollander, Department of Sports and Exercise Medicine, University of Hamburg, Institute of Human Movement Science, Hamburg 20148, Germany; karsten.hollander{at}uni-hamburg ...
1 Department of Surgical and Perioperative Science, Sports Medicine, University of Umeå, S-901 87 Umeå, Sweden 2 Department of Community Medicine and Rehabilitation, Rehabilitation Medicine, ...