In Sweden, approximately 43,000 people have undergone surgery with ileo-, colo- or urostomy. The most common type of stomy is a sigmoidostomy. A large proportion, about 50%, of patients who receive a permanent sigmoidostomy develop a parastomal hernia which may have major impact. There are indications that specific abdominal exercise may reduce the risk of parastomal hernias, but randomized studies are lacking. The aims of the study are: 1. to evaluate the effect of specific exercise to counteract the development of parastomal hernia in sigmoidostomy and the hernia's impact on ostomy function, physical function and quality of life. 2. to examine patients' experience of living with parastomal hernia. The study plans to include 240 patients who on will undergo surgery and receive a sigmoidostomy. These will be randomized to receive only advice according to the usual routine to avoid the development of parastomal hernia or these advice with the addition of specific abdominal muscle training. The training is initiated before the operation and is then carried out during the first postoperative year. Follow-up will be done with a clinical assessment and with measurement of bulge and size of the parastomal hernia manually, with electronic measuring equipment and via computed tomography images. Patients will assess their stoma and stoma function and assess any discomfort and its consequences of hernia via a study-specific questionnaire. Type of ostomy bandage will also be registered. The evaluation will be carried out 6, 12 and 36 months postoperatively. Prior to the start of sub-study a, the planned measurement methods to assess whether a parastomal hernia is present will be tested for validity. In addition, a group of patients (≥15 people) with parastomal hernia will be included in a qualitative sub-study where they will be interviewed about their experiences of the hernia hernia and how it may affect daily life. The present study will be able to answer whether specific exercise can reduce the risk of parastomal hernia. Methods for clinically assessing and evaluating bulging and hernias will be tested and evaluated in relation to patient-reported symptoms. In addition, the study will provide information about the patient's experience of having a parastomal hernia and how it affects daily life and physical activity. The results will provide an increased understanding of parastomal hernias, which may change the follow-up of patients in the future.