Someone just posted a question about sticthes. That's another nagging problem I see a fair amount of in athletes. I've experienced it myself and once lost a race due to this. The following is an article I wrote on this topic many years ago. I've not found anything new to cause me to revise it...
In the early 1980s I trained with a fellow who was plagued by side stitches. I'm sure you've experienced one of these yourself when running. Gradually, a sharp pain in your upper abdomen forces you to slow down dramatically. You jog along gasping for air and pushing on the painful spot. A few minutes later the pain subsides and you cautiously resume your earlier pace.
My friend, an excellent runner, tried everything from stretching to acupuncture to special diets. Nothing helped. He wasn't alone in his quest for an answer. For years, the stitch has been a mystery to everyone including exercise physiologists and the medical community. Here is a possible solution.
It's clear that gravity has something to do with the malady—they are rare in biking or swimming. Sports that involve the up-and-down motion of running are most susceptible. It also appears that most stitches are on the right side of the abdomen, in the area of the liver, the heaviest organ in the gut.
The liver, stomach, and spleen all hang from ligaments attached to the diaphragm, a large, flat muscle in the gut that creates inhalation as it contracts. During running these organs bounce pulling down on the diaphragm, and sometimes, perhaps, causing the gut cramp known as a stitch.
Here's what to do. With a stitch on the right side, exhale when your left foot strikes the ground. This will transfer most of the jarring force away from the afflicted side allowing you to take the stress off of the diaphragm. Give it a try. Several of the athletes I coach have had success with it.