Effects of Aerobic Exercise During the Early Rehabilitation After Ischemic Stroke

The goal of this clinical trial is to study the effects of aerobic exercise during the early rehabilitation after ischemic stroke. The main questions it aims to answer are: * How is the recovery of motor function affected by regularly walking during the first 90 days after an ischemic stroke? * Does regularly walking during the first 90 days after ischemic stroke affect cognition, physical comfort and the immune system? Participants will exert a heart rate controlled walking programme of walking 3-5 times 30-45 minutes per week. Researchers will compare the recovery of the walking group to a control group without any demands regarding physical exercise.