Inclusion Criteria:  Patients with mild TBI defined by the World Health Organization (WHO) Collaborating Center Task Force definition: 1) one or more of the following: confusion or disorientation, loss of consciousness (LOC) ≤30 minutes, post-traumatic memory loss (PTA) ≤24 hours and / or transient neurological focal deficits and intracranial lesions that do not require surgery; 2) Glasgow Coma Scale (GCS) score of 13-15 at least 30 minutes after trauma). 18-60 years with persistent post-commotio symptoms (minimum 3 months maximum 2 years). Reduced tolerance to physical activity/exercise intolerance (self-reported worsening of symptoms such as dizziness and headache during physical activity and exercise).  Exclusion Criteria:  Other neurological or psychiatric conditions (not including anxiety and depression) listed in the medical record. Heart-lung disease, extremity injuries that prevent physical exercise, drug addiction and insufficient understanding of the Norwegian language (unable to follow instructions and/or fill in forms). Normal BCTT.