I've been doing some light yoga off and on for a while. No matter what I do, though, vinyasas are incredibly difficult for me. My shoulders give out very quickly, and it seems like all the stress seems to be going there. I have a few friends who have done it with me (but are all at my level of expertise [that is to say none]) and none of them can really pinpoint anything I'm doing wrong.
For form/ starting in plank (I'll describe the best that I can, hopefully it will help) my legs are straight, feet slightly less than shoulder width...standing distance I suppose? Hands are right underneath the shoulders or very slightly in front.
It's my understanding that hands and legs should not move considerably when going from downward to upward dog, so I keep them stationary when changing positions.
Still, after just a couple vinyasas, I feel like I can barely keep going. I know my shoulders aren't that weak, as I can keep up with shoulder exercises.
Any thoughts/ advice?