You're running along your usual path at a steady clip when suddenly you're gripped with a sharp pain in your side. With each breath, the pain becomes more intense, and you're forced to stop. Looks like you've been temporarily sidelined by side stitch.
No one is actually sure what causes side stitch. It is believed to be a cramp in the diaphragm, the large, flat, muscular membrane that separates the chest and abdominal organs and helps force air into and out of the lungs during breathing. Exactly why the diaphragm spasms, however, remains unclear. It could be the result of tugging on the diaphragm by the ligaments that attach the internal organs, such as the liver, to the muscle. The organs naturally bounce up and down on the elastic ligaments as we run or jump.
If you happen to be exhaling -- which requires the diaphragm to rise and tighten -- at the same time your foot lands during a stride, the liver ends up pulling downward at exactly the same time the diaphragm is highest and tightest in the torso. This tugging and strain could cause the diaphragm to spasm.
Another explanation maybe that exercising intensely decreases blood flow to the diaphragm, causing it to go into spasm. Also, raising the knees to run contracts the belly muscles, which increases pressure inside the belly and presses on the diaphragm from below.
Additionally, during exercise, air tends to get into the lungs more easily than it gets out, so the lungs fill with air and press on the diaphragm from above. The dual pressure may squeeze the diaphragm and briefly shut off its blood flow, resulting in cramping.
Another theory suggests that side-stitch pain results from gas trapped in the large intestine. Exercise tends to speed up intestinal contractions and push gas toward the colon, or the end of the large intestine. If the colon is blocked by a hardened stool, however, cramping can result.
Yet another school of thought holds that side stitch may be brought on by exercising too soon after eating. Additionally, in some people, side stitch may be related to an intolerance of wheat or dairy products. People with such an intolerance may develop side stitch if they exercise within 24 hours of eating wheat or dairy.
Until a definitive explanation and cure for side stitch are found, you can help prevent or halt it quickly using the following home remedies.
Belly breathe. Most episodes of side stitch come from shallow breathing during exercise. While you exercise, try to breathe deeply and slowly, expanding the belly as well as the upper chest.
Try the "grunt" exhale. Making a grunting sound as you exhale seems to help relieve side stitch, possibly because it forces the diaphragm out of its taught "exhale" position.
Slow down. Being out of condition and exercising too intensely causes you to breathe quickly -- and more shallowly. Build your intensity slowly over the course of several weeks.
Stop. Some people, particularly competitive runners, believe you should "run through" a side stitch. However, unless you're in a race, the best idea is to stop completely until the pain subsides.
Use the "one hour" rule. If you've eaten a meal, wait at least an hour before exercising, because a full stomach does appear to cause problems for some people during exercise.
Massage it. Gently rub the area with your hands. Massage relaxes the muscles and helps increase blood flow to the area.
Use the "poke and blow" technique. One way to relieve diaphragm pressure is to push your fingers deeply into your belly just below your ribs on the right side. At the same time, purse your lips tightly and blow out as hard as you can.
Practice running fast. One of the possible causes of side stitch is weak abdominal and diaphragm muscles. To increase endurance and strengthen the diaphragm, try running fast a couple of times a week or inserting a couple of intervals of fast running during your regular, more moderately paced jog.