Apana is the term for the force that removes “stuff” from the body — where “stuff” can mean breath, urine, feces, menstrual fluid, or negative energy. (And probably other stuff too. That list is not intended to be all-inclusive.) Apana is generally regarded as originating in the lower chakras and/or pelvic floor, which then might explain why apanasana primarily involves the movement of the low back and pelvis.
One short-term physical benefit of apanasana is that it offers a supported way to stretch and start to move the low spine without putting a whole lot of stress on the body. This can be a great way to send blood flow to the back muscles and to generally circulate fluids around the body. In the longer term, apanasana may also be involved in other benefits to the physical and energy bodies:
I’m also just going to throw this in here as an aside: While a long-standing practice has done a lot for me physically and mentally, I’m not going to pretend I think it’s a magic cure-all for all people or any given condition. That said, I do think it’s worthwhile to approach ideas with an open mind (open critical minds and open skeptical minds do count!) and for folks to work with those ideas in a way that best serves them.
A variation of the pose involves moving the knees in a circle (repeating both clockwise and counterclockwise), still in connection with the breath. I tend to like this variation because I can adjust my thigh position so that my sacrum is always on the ground and the circular movement massages it, which relieves some of my pelvic tension and sacroiliac joint pain. YMMV with that, of course, but it’s not a bad thing to play with.
Finally, apanasana (either variation) can be a good counter pose either after or in between backbends. So, something to remember for later. 😉