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.
Here are just a few reasons why your baby may have blood in his stool: 1  An anal fissure, which is a small anal tear often caused by passing a hard stool. 2  A food allergy. 3  Maternal blood from delivery or from cracked, sore nipples.  An intestinal 1  infection. An intestinal disorder, such as colitis or intussusception.
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.