<qa>  What is the aim of the study?Patients with idiopathic Normal Pressure Hydrocephalus iNPH have variable difficulties regarding gait, balance, cognition and micturition. A shunt operation will improve these difficulties in most cases. Data suggest however, that they do not change their physical activity postoperatively. Physical training has been shown to be beneficial in patients with similar diseases i.e. Parkinson. The aim of this study is to apply a high intensity physical training program after a shunt operation to see if the patients can improve their physical capacity and ambulatory activity more than patients who only receive standardized written advice about physical training. 