Patients will be randomized into three groups: 1) Intervention I: 12 week exercise program with low-intensity fitness training 3 times per week. 2) Intervention II: 12 week exercise program with moderate to high-intensity fitness training 3 times per week. 3) Control group. The physiotherapists at Primary Care Rehab will perform the submaximal bicycle test and personally design the exercise program in the gym. The patients will have a one-to-one session with the physiotherapists on 2 occasions and afterwards several people will exercise at the same time in the gym.