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.
Blood in Baby's Stool. Babies can sometimes have blood in their stool that is caused by food allergies, a small anal tear or fissure, or even a temporary case of lactose intolerance. It might even be a drop of blood that came from a cracked nipple, which the baby then passed through his system.
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.