I have only taken one yoga class and I loved it! I think I enjoyed it so much because it is so different from running. It is so relaxing and you just do whatever you can, no pressure. I don't always have the time to go to a yoga class, but I am going to try and incorporate a yoga routine into my running plan a few times per week. I tried this one today found at Spark People . All you need is a mat, a chair or yoga block and a towel. You can do this for your post run stretching or, if you want to do this on your non run days, make sure you do a ten minute cardio warm up first.
According to the author Stefanie Romine who is a Certified Ashtanga Yoga Teacher:
"A breath is one full inhalation and one full exhalation through the
nose. Hold each pose for five breaths, or longer if you'd like."