 Background Severe acquired brain injury is usually associated with permanent disabilities in motor skills and cognitive functions that inhibit patients level of functioning, communication, participation in social activities and ability to work Faul et al 2015, McLafferty et al 2016. Patients with severe brain injury often have reduced level of consciousness in the early stages after the incident. Studies have shown that the autonomic nervous system can be affected in these patients, shown by analysis of the heart rate variability in the low frequency domain Riberholt et al 2016, Vistisen et al 2014. Signals from motor- and sensory cortex can influence sympathetic and parasympathetic activity and thus be a part of the cardiovascular adaptation during function Sequeira et al 2000. Aerobic exercise has been demonstrated to be effective regarding to autonomic cardiovascular regulation among healthy workers Hallman et al 2017. 