Pain is a message to our brains, expressed by a negative sensation and transmitted through nerve fibers, that an illness or injury is affecting a part of our body.
In the case of a side stitch, this is a very specific but temporary type of pain that is fairly common among runners, and tends to occur more in athletes new to running longer distances. The muscle that is the main cause of side stitches is the diaphragm, which is dome-shaped and is located at the bottom of your ribs. This muscular sheet separates your abdominal cavity from your chest cavity, and is mainly responsible for inhalation.
As you run, your abdomen places a greater than normal amount of pressure on your diaphragm from below. At the same time, a rapid breathing rate causes the lungs to also place pressure on the diaphragm from above. This essentially pinches the muscle of the diaphragm, causing decreased blood flow and muscle spasms, which results in the side stitch sensation. As a newer runner continues to train and his or her body adapts to the physical demands of running, breathing becomes more routine and side stitches should occur less often and hopefully one day will be eliminated completely.
Veteran runners can also experience side stitches, and the main cause is usually food. When a runner eats too large of a meal too close to a workout or a race, this also puts pressure on the diaphragm, resulting in a side stitch.
If you experience side stitches, there are a few things you can do to help prevent them. Slowing your pace instead of pushing yourself too hard will help prevent the muscle spasms that cause this pain. Strength training for the core, such as traditional and side planks, help strengthen this region of the body. Spacing out your meals and consuming only a reasonable amount of glucose-based gels and drinks can help prevent stomach discomfort and unnecessary pressure on the abdomen. Adopting a new breathing pattern can help control the movement of the diaphragm muscle.
If you get a side stitch while out on a run, you can slow your pace until the pain subsides. If it continues, stop for a moment, slow your breathing, and stretch out your side. Resume running at a slower pace so that your can finish your workout strong and pain free.