I am a RYT 200HR YA+ registered Yoga instructor. I have been exploring wilderness in a lightweight style for the last 3 years, and in a much heavier way all my life. I am new to Backpacking light and I am happy I found this great resource and I hope i contribute to it. I also hope I don't have too many typos or link errors :)
Given that this thread combines those two interests I figure I might have some knowledge others may find useful.
First, Yoga is a lifestyle and a philosophy for understanding the world, Asana (postures) are what we commonly know in the west to be the "stretches" Properly executed the practice of Yoga is one of the best ways I have found to stay mentally and physically fit for life on and off the trail.
Some of the best "stretches" are the Sūryānamaskāra A&B that was already mentioned, They warm your muscles up and clear you mind for the day. Practiced with proper vinyasa (breathing) the Sūryānamaskāra is one of the best and safest calisthenic exercises you can perform.
**As a note here, I say calisthenic because what we practice in the west and arguably all over the world as "yoga" today is largely a amalgamation of ~100 years of Indian calisthenic tradition. Anyone who is interested in this history should read Mark Singleton's "Yoga Body: The Origins of Modern Posture Practice".
Getting back on topic, those who are seriously interested in the practice of Yoga, to rehab, to exercise, to gain a clearer mind, should consult a physician before undergoing any physical practice, especially if you are recovering from an injury, and/or if you have any outstanding medical concerns. Notably, blood pressure issues are of special concern.
The type of Yoga that I practice is called Ashtanga Yoga, named for its 8-limbed approach. I would suggest going to my teachers website Ashtanga Yoga Canada, not just because they are my teachers, but also they have put together a set of very clear (and FREE) resources about Ashtanga Yoga, including "posture posters" that show you what, and how to practice. There is also youtube! what a great resource. Also they have a website that is specifically dedicated to their Shala Ashtanga Yoga Victoria
I would also suggest to find yourself a dedicated, kind, and disciplined teacher in your area to guide you through the first few sessions of practice and if money is an issues at least return once a month for a "update" so to speak, on your practice.
This is only my humble opinion on my very limited experience with the practice of Ashtanga Yoga (~8 years). It is a lifelong and difficult process of self-inquiry and self advancement, it is ultimately selfish, but deeply rewarding on many levels.
If anyone wants any more specific information or guidelines for how to go about searching out a teacher in your area I would be more then happy to consult with via e-mail. Send me a PM and we can go from there.