2.2. Participants. About half of the participants were recruited from the Capital Region and the other half from other parts of Denmark. Thereby the population is nationally representative and strengths external validity. The eligibility
criterion was employees performing office work for at least half of their working hours. The exclusion criteria were (i) hypertension (systolic BP > 160, diastolic BP > 100) or
cardiovascular diseases, (ii) symptomatic herniated disc or severe disorders of the cervical spine, (iii) postoperative conditions in the neck or shoulder region, (iv) history of severe trauma, (v) pregnancy, (vi) or serious disease.