Dear
Marissa,
First, I'd like to start by saying that I am not a doctor or coach, just a Web site editor who's spent lots of time with running kids. I also read a lot!
The theories on side stitches are numerous. Here are a few:
DIET
Watch what you eat before you run. Be careful with dairy products and foods that are difficult to digest. Some kids do better running on a fairly empty stomach.
As for hydration, some sources say perhaps you are too hydrated, others say perhaps you aren't hydrated enough.
ABS
Some coaches claim that strengthening abdominal muscles can help with prevent the side-stitch. Strengthening abs by doing crunches and other ab work will also help with lower back muscles.
SPEED
Some kids cramp in races when they don't in training. One of the major differences is their speed. Sometimes slowing down can prevent cramping.
BREATHING
Another theory is that your method of breathing, while running, may not be optimal. One of the most tried and true methods for making that cramp go away is controlled breathing. When it comes on, breathe in deeply and let your breath out very slowly, like you are blowing out a candle. Repeat this until the cramp or stitch disappears.
Another alternative is putting pressure on the cramp with your hand while you run. I tried this yesterday and it worked for me.
LIGAMENTS
The explanations get more and more complex. Another is that your ligaments that are attached to your liver get too stretched out (Gabe Mirkin, MD Side Stitch ) See this article for an analysis of right vs. left foot hitting the ground. etc.
Marissa, you need to experiment with what works for you and perhaps it might be wise to discuss this problem with your family doctor.
Best of luck. Please keep us at KidsRunning.Com posted on your running.