Understanding Mechanisms of Normal and Disordered Defecation

Inclusion Criteria * Male and female volunteers aged 18-80 years. * Able to provide written informed consent before participating in the study. * Able to communicate adequately with the investigator and to comply with the requirements for the entire study. * Individuals with chronic constipation for 1 year, with 2 or more of the following symptoms for 3 months or longer: \<3 bowel motions/week, straining ≥ 25% of time, hard or lumpy stools ≥ 25% of time, anal digitation ≥ 25% of time, incomplete evacuation ≥ 25% of time, feeling of anorectal blockage ≥ 25% of time. * Able to provide written informed consent before participating in the study. * Able to communicate adequately with the investigator and to comply with the requirements for the entire study. Exclusion Criteria * Clinical evidence of significant cardiovascular, respiratory, renal, hepatic, gastrointestinal, hematological, neurological, psychiatric or other disease that may interfere with the objectives of the study and/or pose safety concerns. * Current symptoms of a functional gastrointestinal disorder assessed by questionnaire. * Putative risk factors for pelvic floor trauma: i.e. six or more vaginal deliveries, birthweight \>4500gms (macrosomia), or known 3rd or 4th degree perineal tear. * Medications that are likely to alter gastrointestinal motility: e.g., opiates and anticholinergic medications; a stable dose of thyroxine and low doses of tricyclic agents (e.g., up to amitriptyline (50 mg daily). * Active rectal inflammation, cancer; perianal sepsis; history of pelvic radiation, rectosigmoid surgery or inflammatory bowel disease.\* * Anxiety or depression as assessed by the Hospital Anxiety and Depression Questionnaire. * Pregnant women, prisoners and institutionalized individuals.