What causes...

 the pain in your side right under your rib cage when you run?  I used to run many, many years ago when I was in high school.  I have recently started running again and tonight I pushed it a little and got that pain in my right side under the rib cage.  In High School I remember putting my arm over my head and just walking it out.  Never really thought much then about what it was.  I felt that again tonight.  Anyone know what causes it and what can be done to prevent it?

The latest research has it pinned as a stretching of the ligaments around the liver when you run in a particular rhythm.  I have found that it works well to exhale all your air every two or three breaths when you feel it comming on.  That way, you get new air in your lungs and it disrupts the rhythm that causes the stretching.  The article that I read says to stop and walk while pressing under your ribs.  After a bit, resume running. 

Most people breathe in tune with their running steps.  In for two steps and out for two or in for three and out for three.  Another thing that I do when I feel the stich comming on is to breathe in for two steps and in for three steps.  According to the article, this also disrupts the rhythm that causes the pain.

 Thanks again for the info.  I changed the rhythm of my breathing tonight when I first started to feel the stitch coming on and it worked like a charm.  I'm so excited that I jogged a full mile tonight without stopping.  I'm only 3 months out of surgery and never ever thought I'd be running again.  My quads are a little sore so I'm just doing some gentle stretching, but I'm so excited to keep running and keep getting healthier.  

Glad to hear that it worked.  I actually just made all that up.  It was a total guess! 
I'm kidding.  I think I read that one on Runners World.  Reading every word that mag has printed for the last 4 years has finally paid off.  ;-)

 Thanks Scott!  I'll try both of those techniques if I need to when I run next.  That makes a lot of sense about the ligaments around the liver.  That's right where the pain is.