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.
2. Black or tarry stools (Melena) - the passage of black, tarry and foul-smelling stools; can be an indication of digested blood in the stool. Other causes are, iron deficiency anemia, cirrhosis, colorectal cancer, disseminated intravascular coagulation, peptic ulcer, or stomach cancer.. Black or tarry stools (Melena) - the passage of black, tarry and foul-smelling stools; can be an indication of digested blood in the stool. Other causes are, iron deficiency anemia, cirrhosis, colorectal cancer, disseminated intravascular coagulation, peptic ulcer, or stomach cancer.