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.
You should call your pediatrician if your infant has: Signs of dehydration (a sunken fontanel, few wet diapers, dry eyes when crying, dry mouth, sunken eyes or lethargy) Mucus or foul odor in three or more diarrhea stools (for infants one month of age or younger) Blood in the stool.