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.
Blood in stool is a hint that bleeding is present in the digestive tract. The bleeding is usually described either as dark in color or bright red blood on toilet tissue or stool. But in some occasions, the presence of blood can only be determined by a procedure known as fecal occult blood test. The causes of bloody stool can also be determined using several other diagnostic methods.