There's no escaping it: If you study anatomy and physiology and you want to apply these concepts to yoga, your practice will change.
Let's take the image above as an example. I can rather easily put both feet behind my head if I use my hands to help, but with no hands this is as far as I can lift those legs. We get used to using external forces like our hands, straps, or gravity to PULL us deeper into poses that we could never get into without those forces.
Why? How far is far enough? Do we only stop when it hurts?
Range of Motion (ROM) can be broken into two distinct categories:
For example, the way a dog scratches its head is active in the back leg, whereas a human grabbing their foot and slinging it behind their head is passive.
Your joints can move pretty far if you force them to move by "sinking into gravity" or "pulling yourself deeper" but your poor joints don't have local musculature supporting the journey! If you are not in control of the movement, who/what is? GRAVITY, LEVERAGE, TORQUE, POTENTIAL ENERGY, and other forces of physics are in control, and they don't care at all about your wellbeing.
aROM vs pROM is a very simple and effective way to look at your practice and keep it safe & effective. If you just keep this one simple principle in mind when you practice or teach yoga, it will keep you and your students safe. Are you in control of your joints in a pose, or is gravity, or leverage, or torque? Consider also that if you couldn't get INTO the pose without these forces, you can't get OUT without them either. Meaning once again you aren't in control, physics is.
If your reasons for practicing yoga are to be a contortionist, or to garner more instagram "likes" then this is bad news. If you are practicing for literally ANY OTHER REASON, this is liberation from the pressure to out-stretch and out-bend your classmates and peers. You have permission to use all of the blocks, to put your knees down, to go LESS DEEP instead of deeper, and to care more about the depth of your breath and consciousness than the depth of your pose. Be free! Be safe. Be healthy.
Exercise a small restraint to unlock a new world of integrated stability in your practice. For examples of how to modify common poses for greater tensegrity, see my instagram @shapeshiftwellness. How do YOU modify your practice due to learning anatomy?