For Michelet, the Renaissance was more a development in science than in art and culture. He asserted that it spanned the period from Columbus to Copernicus to Galileo; that is, from the end of the 15th century to the middle of the 17th century.
Other researchers believe that side stitches are caused by stretching the ligaments that extend from the diaphragm to the liver. When a runner or walker pounds the surface while breathing in and out, he or she stretches these ligaments, and that causes the pain.
What Causes a Side Stitch. While there is still no definitive explanation for the cause of a side stitch, there are several very convincing theories. The majority of the researchers believe that it has a lot to do with what we eat before we exercise. Several studies agree that ETAP is most common in running and swimming.