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 more serious causes of blood in stool include: 1  Crohnâs disease â Crohnâs disease causes inflammation of the digestive tract lining and can lead to severe diarrhea and abdominal pain. 2  Colon Polyps â Colon polyps are benign growths, or clumps of cells, that form along the lining of the colon.