Concentric contractions: A concentric contraction is a type of muscle contraction where the length of the muscles shorten while undergoing tension. For example, when you pick up a curl bar and perform a biceps curl, the length of your biceps muscles shorten.
Causes of Blood in Stool. 1  Anal Fissure. If no diarrhea, most of these children have a small tear in the anus. 2  Strep Skin Infection. A Strep skin infection around the anus can also cause blood-streaked stools. 3  Bacterial Diarrhea. If also has bloody diarrhea, a gut bacterial infection may be the cause.  Red, but not Blood.
Other conditions that can cause blood in the stool include: 1  Hemorrhoids. 2  Anal fissures. 3  Colon polyps. 4  Peptic ulcers. 5  Ulcerative colitis. 6  Gastroesophageal reflux disease (GERD) . 7  Crohn's disease. 8  Use of aspirin or nonsteroidal anti-inflammatory drugs (NSAIDs) .olorectal cancer affects the large intestine (colon) and the rectum. There are three kinds of stool tests: 1  Fecal occult blood test (FOBT). 2  For this test, you put tiny samples of your stool on a special card or cloth and send it to a lab. 3  The lab uses chemicals to find blood that you can't see with the naked eye.