Inclusion Criteria: Two groups of subjects will be studied - normal healthy subjects and patients with chronic constipation.  Normal subjects:  Inclusion criteria *Normal defecation pattern, i.e., bowel movement once every day or other day without excessive straining and sense of complete evacuation.  Exclusion Criteria:  Subjects not willing to consent and undergo the specified tests in this study Pregnant women Subjects with concurrent fecal incontinence and constipation symptoms Chronic diseases Taking medications that affect anorectal function History of anorectal surgery or bowel resection.  Constipation patients:  Inclusion Criteria:  Rome IV diagnostic criteria will be used to diagnose chronic constipation. Patients must have experienced at least two of the following symptoms over the preceding 3 months:  Fewer than three spontaneous bowel movements per week, Straining for more than 25% of defecation attempts, Lumpy or hard stools for at least 25% of defecation attempts, and  sensation of anorectal obstruction or blockage.  -  Exclusion Criteria:  Patients not willing to consent and undergo the specified tests in this study pregnant women and patients with concurrent fecal incontinence History of anorectal surgery or bowel resection.