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.
There are likely to be other possible causes, so ask your doctor about your symptoms. 1  Blood in stool - see causes of blood in stool and rectal bleeding for various possible diagnoses. 2  Certain foods Iron supplements. 3  Stomach bleeding - usually causes darker or black blood in the stool. 4  AVM. more causes...Â».