This guarding effect is translated by the body and muscles cramps. It is the leading cause of absenteeism from work and school. Doctors have now finally located the culprit. Through research they have isolated a class of chemicals called prostaglandins, which are produced by portions of the nervous system and in various other parts of the body. Studies have shown that women with severe menstrual pain have considerably higher concentrations of prostaglandin in their menstrual fluid.
Prostaglandin acts as a stimulators to the muscle tissue within the uterus.
The prostaglandins cause the muscles of the uterus to tighten because it slows the oxygen transfer from the blood vessels to the uterus. The pain associated with the cramping is very close to what athlete's experienced when they have over trained. When there is a lack of oxygen to the muscles they will begin to shorten thus producing a cramping effect that produces an ache or pain depending on the amount of shortening. Once the menstrual flow begins, the prostoglandins are removed and the muscle begins to elongate again and the pain will begin to go away. Now you know why some women find relief when using a heating pad or a hot water bottle.