Inclusion Criteria for Controls:

• Healthy 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.

Inclusion Criteria for Constipated Patients:

• Male and female volunteers aged 18-80 years.
• 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 for Controls (items marked with an asterisk also apply to patients):

• 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 andanticholinergic 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.*