Regina Z.
None! (At least for the Sun Salutation) Think of the poses as ponds along a river. You flow between them, only holding each for a few seconds while you breathe.
For me, the "Sun Salutations Intro" was WAY harder than the actual "Sun Salutations" timed yoga program on this app. I was trying to hold each position for 30 seconds and… WHEW.
Personally, I still don't think I'm doing the 8-point bow correctly. If there's a pose in any yoga routine that makes you feel like you need to take a breather, pause the guide and rest for 60 secinds tops.
Now, if there's a pose that HURTS (not a stretchy/pulling sensation, but physically crampy or sharp) try googling a modified version of the pose to make it easier on whatever body part is suffering. Common modifications may lighten the load on knees, the back, or other places where previous injuries cause stiffness.