What causes side aches?

I agree with Karen, but only from personal experience. My stitch appears to be in my diaphragm, and I've learned to use it as a governor. When I feel it come on, I know I'm reaching the point where my effort is approaching the limits of my fitness, and have learned to back off at that point.

I know of no scientific basis for this, but it works like that for me.

There are two reasons why I get side stitches:

1). Irregular/Shallow Breathing while running
2). Having too much in my stomach while I am trying to run

In either case, they rarely slow me down as I now know how to make them go away fairly quickly.

I don't often get them because of a full tummy any more and if I do, like Karen and Bear, it is usually caused by pacing too hard. (Causing my GI System to Shut Down) I can usually tell what the cause is by what side of my belly the stitch is hitting. Alternatively, I never eat anything and rarely even drink for shorter distance races. (Like 5k - 15k)

To get rid of them, what I do is focus on taking full and complete breaths and belly breath.

More often then not for me, it is caused by shallow/irregular breathing. If I focus on a regular breathing rhythm with complete breaths from the belly, they usually go away within a 100 yards or so. I have found that speeding up also helps as it increases my oxygen needs and forces me to take more complete breaths.

If I find that my GI system was completely shut down, the only thing left for me to do is stop eating/drinking, slow down and try and push through it as well as focus on good breathing. (And if I am lucky, it will go away)

Mine comes from the monkey that seems to be on my back after mile 15...

I cruising along, doing great, feeling good, going fast, but he's out there hiding in some bush or tree.  I hit mile 14 or 15 and he gets me...

OR, it could be I'm pushing my limits of fitness.  But I think it's the monkey.

Totally agree.  He goes for my legs all the time in longer races.

(evil-monkey.jpg)

Yep, that's him.  I could pick him out of a line-up any day...

You just might be.    I get one in the front of my right shoulder though, so I'll be weird with you.  All I have to do is drop my hands to where I feel them brushing my waistline as I run and slow down for a minute or so for the pain to go away. 

9mm?