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: Breast fed babies can have mucosy, seedy stools; it is normal. Blood in the stool needs confirmation. Swallowed blood from breast can cause darker bloody stools. Baby's stool needs to be tested- hemoccult test to see whether it is blood.