I'm deleting the post on yoga teachers because it has become a magnet for spam. But I want to remember the suggestions:
This from royalbananafish:
Have you read Doug Keller's work on pranayama? www.doyoga.com I think is his website.
IMLHO (that's "In My Least Humble Opinion"): Intentionally slowing our breathing (or altering it in other ways) as a practice has an effect on our parasympathetic breathing, just like practicing a yoga posture repeatedly has an effect on the way you sit or stand. So I think the point isn't trying to switch from one type of response to another, but more to practice in such a way that the response alters itself. (Does that make sense?)
Also, there are varying ways to extend your exhalation, and the amount of time you spend practicing and how quickly you attempt to lengthen it (er, meaning the length of the practice period in which you attempt to extend from, say, "normal" to something much longer) all have an effect. I find that trying to jump into too much (advanced/whatever) a practice makes me much less relaxed. The teachings I have experienced on pranayama all have a beginner mode where you are extending just a little bit more, or holding your breath for just a little bit, and students are expected to practice that beginner practice for quite some time before gradually moving into more difficult practices (longer inhale, longer exhale, longer retention, etc.).
One other thought is that the mind does interesting things when you change your breathing. Maybe your feeling not as relaxed in intentional exhalation extension indicates something else? I'm thinking anything from needing in inhale a greater volume of air to a mind reaction that you're doing it wrong or need to breathe or something. Just thoughts, YMMV.
and another:
Me again, posting from work (which won't let me sign in for some reason). Okay, now that I se what you are driving at, your best resources are "Yoga as Medicine" by Dr. Timothy McCall, and David Coulter's "Yoga Anatomy." You might also try looking into past and future publications in the research journal published by IAYT.
responses to same post @ yogateachers group
This from royalbananafish:
Have you read Doug Keller's work on pranayama? www.doyoga.com I think is his website.
IMLHO (that's "In My Least Humble Opinion"):
Intentionally slowing our breathing (or altering it in other ways) as a practice has an effect on our parasympathetic breathing, just like practicing a yoga posture repeatedly has an effect on the way you sit or stand. So I think the point isn't trying to switch from one type of response to another, but more to practice in such a way that the response alters itself. (Does that make sense?)
Also, there are varying ways to extend your exhalation, and the amount of time you spend practicing and how quickly you attempt to lengthen it (er, meaning the length of the practice period in which you attempt to extend from, say, "normal" to something much longer) all have an effect. I find that trying to jump into too much (advanced/whatever) a practice makes me much less relaxed. The teachings I have experienced on pranayama all have a beginner mode where you are extending just a little bit more, or holding your breath for just a little bit, and students are expected to practice that beginner practice for quite some time before gradually moving into more difficult practices (longer inhale, longer exhale, longer retention, etc.).
One other thought is that the mind does interesting things when you change your breathing. Maybe your feeling not as relaxed in intentional exhalation extension indicates something else? I'm thinking anything from needing in inhale a greater volume of air to a mind reaction that you're doing it wrong or need to breathe or something. Just thoughts, YMMV.
and another:
Me again, posting from work (which won't let me sign in for some reason). Okay, now that I se what you are driving at, your best resources are "Yoga as Medicine" by Dr. Timothy McCall, and David Coulter's "Yoga Anatomy." You might also try looking into past and future publications in the research journal published by IAYT.