BACKGROUND: Neck and shoulder complaints are common among employees in sedentary occupations characterized by intensive computer use. Specific strength training is a promising type of physical exercise for relieving neck and shoulder pain in office workers. However, the optimal combination of frequency and exercise duration, as well as the importance of exercise supervision, is unknown. The VIMS study investigates in a cluster randomized controlled design the effectiveness of different time wise combinations of specific strength training with identical accumulated volume, and the relevance of training supervision for safe and effective training. METHODS/DESIGN: A cluster randomized controlled trial of 20 weeks duration where employed office workers are randomized to 1 x 60 min, 3 x 20 min, 9 x 7 min per week of specific strength training with training supervision, to 3 x 20 min per week of specific strength training with a minimal amount of training supervision, or to a reference group without training. A questionnaire will be sent to 2000 employees in jobs characterized by intensive computer work. Employees with cardiovascular disease, trauma, hypertension, or serious chronic disease will be excluded. The main outcome measure is pain in the neck and shoulders at week 20. TRIAL REGISTRATION: The trial is registered at ClinicalTrials.gov, number NCT01027390.