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.
Sometimes, the blood may not even be visible on the stool, and this is termed occult gastrointestinal bleeding. By far, the most common causes of visible blood in the stools are diverticulitis and hemorrhoids. Other conditions and situations that can cause blood in the stools include: colon cancer. non-cancerous growths, such as polyps. intestinal infections (bacterial enterocolitis) that can be caused by foodborne pathogens, such as salmonella and E. coli.