Background: Abdominal bloating is a frequent and bothersome complaint in patients with functional gut disorders without satisfactory treatment to date. Recent data from our laboratory indicate that abdominal distention in these patients is produced by abdomino-phrenic dyssynergia: diaphragmatic contraction associated with abdominal wall relaxation (particularly the internal oblique). In analogy to other clinical situations (e.g. functional outlet obstruction, rumination or aerophagia) behavioral treatment by means of biofeedback might be equally effective in these patients. The investigators hypothesized that abdomino-phrenic coordination and abdominal distention can be controlled by biofeedback techniques.