NINJA BREATHING!
Ok, so... let me put it like this: You do "double breaths", where instead of breathing in or out normally, you do it in two half breaths: Breathe half in twice, breathe half out twice. Get it? Now the secret is how you stack it. You breathe like this:
Double breath in, normal breath out. Normal breath in, double breath out. Normal breath in, normal breath out. Repeat.
Or, in a way that (to me at least) shows the pattern a bit more clearly:
I2 - O1 - I1 - O2 - I1 - O1 - Repeat
Legend: I = breathe in ; O = breathe out ; 1 = normal breath ; 2 = "double breath"
Now don't ask me how this is supposed to make things better. But it works, at least for me. Whether it actually somehow improves your breathing, or whether it's just a self-hypnotic trick I don't know. But I ran, breathing normally, for about one-third of the way. Kept getting sidestings. I then tried breathing
like a ninja (because I remembered), and the sidestings went away. I even found that I could increase my pace quite a bit. Maybe it's because you have to concentrate so hard to keep breathing like that (just try it and you'll see), your breathing becomes deeper, more focused. Or whatever. Seems to work at least.
Now ninjas, far from just
flipping out and killing people ALL the time, usually were used as spies and thieves. If discovered, they had to be able to run from pursuers, sometimes over long distances. I can see how special breathing techniques came in handy.