Esophageal motility testing determines how well the muscles of the esophagus are working. If you feel like having any of gerd symptoms you should consult your doctor. For motility testing, a thin tube (catheter) is passed through a nostril, down the back of the throat, and into the esophagus. On the part of the catheter that is inside the esophagus are sensors that sense pressure. A pressure is generated within the esophagus that is detected by the sensors on the catheter when the muscle of the esophagus contracts. There is a circular band of muscle (a ‘sphincter’) at the junction between the oesophagus and stomach. This relaxes to allow food down, but then normally tightens up and stops food and acid leaking back up (refluxing) into the oesophagus. In effect, the sphincter acts like a valve.