It’s efficient! Why would I waste so much time at the gym working each part of my body separately when I can connect all of the dots and do it all at once with yoga? No amount of lifting weights is going to make my arms as strong as holding up my own body weight in yoga. Also, practically everything you do in yoga is engaging your core, from to moving from pose to pose, using your core to stabilize your body. And in different inversions and arm balances, yoga allows you to raise your heartbeat, strengthen your muscles, and lengthen them out all at once. How’s that for efficiency?
It can count as cardio. All you have to do is try a few sun salutations or any flow at a good, steady pace, matching your breath to your movement. Or, if you are a bit more adventurous, try some Kundalini kriyas (like the Kundalini frogs in the in the step by step pose.
https://www.easyflexibility.com/blogs/yoga-flexibility-pearls/the-psoas-muscle
