 The study will be a randomised and controlled study with randomisation to either an systematic aerobic exercise intervention or an educational programme on exercise and physical activity. Both interventions are in addition to standard treatment, and will last 1 year. The exercise intervention will consist of 2 supervised exercise sessions per week in the complete duration of the study, while the standard treatment plus exercise education program will consist of 4 educational sessions on the health benefits associated with exercise and physical activity held every third month throughout the intervention period. The training in the exercise group will be aerobic exercise running, cycling, rowing or on a cross-trainer planned by exercise physiologists and performed in a progressive manner. To allow handling of a large number of participants, who is also geographically spread, the exercise intervention will be locally anchored, but at the same time supervised by student employees from Section for Sports Science and controlled by internet- and telephonic communication. In addition to the two intervention groups, data from The Danish MS registry will serve as population based standard treatment control data. All groups will be followed up 1 year after cessation of the interventions. 