The Magnetic Tracking System consists of a 4 x 4 matrix of sensors positioned with respect to the anatomical reference points. Before measurements, the matrix is calibrated by offsetting the earth's and environmental magnetic fields. During the experiment, the magnet coordinates are continuously monitored and transmitted to a computer for processing and storage. Respiratory artifacts will be filtered out. Digestive movements will then be classified as 1) non-propulsive or 2) propulsive and transformed into either trajectory or dynamic graphs of the digestive motility.