The objective is to determine the length-tension properties of the anal sphincters using Fecobionics in normal subjects and FI patients during anal distension and during simulated evacuation. Fecobionics has the consistency and shape of normal stool and can record pressures, cross-sectional area, orientation and viscoelastic properties of the anorectum and can map the geometric profiles during evacuation, and thereby provides multi-dimensional measurements of pressures, deformability, and topographic changes. Fecobionics combines several existing tests to provide novel insight into anorectal function. The purpose for the development was to overcome the technological controversies and disagreement between various tests and unphysiological test conditions. The aim was to imitate defecation as much as possible to the natural process. Fecobionics was developed to simulate stool and to provide the driving pressure and resulting deformations of stool along with a measure of an objective anorectal angle during defecation in a single examination. Fecobionics makes it possible to describe objectively, without disturbing the defecation process, the opening characteristics and pressure signatures during initial entry into the relaxing anal canal. The overall goal is to provide mechanistic understanding of defecation in health and defecatory disorders. It exceeds previous attempts to make artificial stool for evaluation of defecation (BET and FECOM) and integrates other technologies as well. It was designed to have a consistency and deformability of Type 4 (range type 3-5) on the Bristol stool form scale. The range from types 3-5 is found in 70% of normal subjects. A major novelty is that Fecobionics measures pressures in axial direction; i.e., in the flow direction.