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.
Causes and Background Information. Causes of Blood in Stool. Anal Fissure. If no diarrhea, most of these children have a small tear in the anus. This is called an anal fissure. Anal fissures usually are caused by passage of a large or hard stool. This is the cause in 90% of children with blood in the stools.