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.
Blood in stool. Find possible causes of blood in stool based on specific factors. Check one or more factors on this page that apply to your symptom. 1  In or on the stool. 2  In toilet bowl or on toilet tissue. 3  Drinking alcohol or caffeine. 4  Eating certain foods. 5  Straining during bowel movements. 6  Drinking more water. 7  Eating certain foods.