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.
Blood in Baby's Stool. Babies can sometimes have blood in their stool that is caused by food allergies, a small anal tear or fissure, or even a temporary case of lactose intolerance. It might even be a drop of blood that came from a cracked nipple, which the baby then passed through his system.
Rectal Bleeding Symptoms and Causes. Blood in the stool can be bright red, maroon in color, black and tarry, or occult (not visible to the naked eye). Examples of causes of blood in the stool are: Hemorrhoids. Cancer. Anal fissures. Crohn's disease. Ulcerative colitis. Anal cancer.