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.
Common Causes of Blood in the Stool. 1. Hemorrhoids: One of the most common causes of blood in the stool is that it is the result of a hemorrhoid that has started to bleed. Hemorrhoids appear when blood vessels in the rectum or anus become swollen and inflamed. Bleeding from a hemorrhoid is typically bright red in color.