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.
Here are just a few reasons why your baby may have blood in his stool: An anal fissure, which is a small anal tear often caused by passing a hard stool. This is the most common cause. A food allergy. Maternal blood from delivery or from cracked, sore nipples. An intestinal infection.