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.
Your baby's stools may be flecked with blood if she's constipated. This is because straining can cause tiny splits in the skin around her anus (anal fissures). These bleed when she has a bowel movement. Sometimes it could be a sign that her intestines are irritated by an infection or allergy. Always get any blood in your baby's stools checked out by your doctor. Take a look at our baby stool photo gallery to see what's normal and what's not.