1. Institute of Sports Science and Clinical Biomechanics, University of Southern Denmark, 5230 Odense, Denmark
2. Institute of Regional Health Research, University of Southern Denmark, 5230 Odense, Denmark
3. National Research Centre for the Working Environment, 2100 Copenhagen, Denmark
4. Department of Nutrition, Exercise and Sports, University of Copenhagen, 2200 Copenhagen, Denmark
5. Department of Occupational Medicine Køge Hospital, 4600 Køge, Denmark
6. Danish Headache Center, Department of Neurology, Glosrtup Hospital, University of Copenhagen, 2600 Copenhagen, Denmark