The Yuins are NOT appropriate for running, in my experience with the PK-2s.
You'll be constantly trying to keep them from falling out.
Yes, YMMV, but I find I can rarely wear the Yuins for anything but sitting or easy walking.
Without the little sock covers, I can't keep them on at all; the U.S. distributor ignores requests to sell replacement covers. He's deleted threads on the subject on his portion of Headfi. Some find the RS versions of these covers a good alternative. I found them to be both overpriced and unsatisfactory.
Soooo....Consider the Senn sport models or perhaps the Koss KSC models 35 or 75.
The Koss won't shut out all sound, and will allow you to remain alert to what's happening around you. When wearing any headphone for outside running, you need to be able to hear cars, dog and other people.
Hope that helps.