Background. Abdominal distention is produced by an abnormal somatic postural tone. The authors developed an original biofeedback technique. In a randomized, placebo-controlled trial the authors demonstrated the superiority of biofeedback over placebo for the treatment of abdominal distention. However, the technique is technically complex and unpractical. Aim. To prove the efficacy of a noninstrumental biofeedback technique, transmitted by a standard training program, for the treatment of abdominal distension in different centers. Selection criteria. Episodes of visible abdominal distension. Intervention. Patients will be randomized into biofeedback and placebo groups. Three sessions of either biofeedback or placebo intervention will be performed during the first 3 weeks of the intervention period. Biofeedback: Patients will be taught to control abdominal and thoracic muscular activity by providing instructions using an original video support. In each center one operator will receive a standard training on how to deliver the noninstrumental biofeedback treatment. Patients will be instructed to perform the same exercises before and after breakfast, lunch and dinner during the 4-week intervention period. Placebo: Sham measurements of abdominal and thoracic motion will be performed, and a pill of placebo containing 0.21 g glucose will be administered; patients will be instructed to take a pill of placebo before breakfast, lunch and dinner during the 4-week intervention period.