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.
My baby has blood in her diaper. The same maternal hormones that cause swollen testicles and labia are also responsible for the bloody vaginal discharge that newborn girls sometimes have. Don't worry if you see a small smudge of blood or bit of staining on your baby's diaper in the first weeks of life.