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.
What causes a baby or toddler to have bright blood in the stool (poop, poo) 1  An infant who is having bouts of screaming and drawing up the legs, maybe with vomiting as well, who then passes what looks like red currant jelly in the bowel motion may have intussusception and you need to see your doctor urgently - read more.