Assuming the spine is at least somewhat warm a forward fold is generally a good erector spinae stretch prior to more core strengthening work. Done with a mind toward lengthening the spine, rather than simply rounding it forward, it can release compression and create more space inside the spine. For me, at least, this spinal length mitigates neck, shoulder, and hip tension in addition to aiding back pain. It’s not a miracle cure, but it is something.
Uttanasana (intense forward fold) has at least one similarity with triangle, at least as I’ve practiced it and seen it practiced: it’s considered kind of a big deal to be able to reach the floor above (or underneath?) all else. So before showing or discussing the asana, I think it’s important to reiterate the idea that enlightenment is not on the floor; rather, it’s inside your body and your experience.
For me, the most accessible way to make uttanasana about spinal length is to bend my knees. Reducing the stretch in my hamstrings (which are attached to the lower side of my pelvis) lets me find a little more comfortable length and stretch in my erector spinae (which are essentially attached to the upper side of my pelvis). Another option is to use various props — like a block, a bolster, a chair, or a couch seat — to sort of bring the ground up to the level of the arms and the torso. To be honest, even as someone with a lot of spinal/pelvic/hamstring flexibility, I don’t fully straighten my legs in this posture until I’m most of the way through a pretty intense heat-building practice. Up to that point, I get the same benefits with slightly bent knees; plus, I know it’s safer for my knees and my spine, which is always a bonus.
One reliable-for-me way to determine whether my spine is lengthening rather than rounding down is whether the front of my torso feels relaxed against the fronts of my thighs. And I say it this way on purpose. As someone with girth to both my belly and my thighs, I find that I can have my torso touch my thighs without relaxing along them. My abs are still engaged a little bit here — enough to support my spine so it can safely lengthen and relax — but the energy of the pose is first about stacking my spine to create length and then using my abs and my thighs to support that.
Particularly when utilizing uttanasana as a warm up, I prefer to do so with a vinyasa. Not only does this increase muscle heat and circulate fluid around the body, but moving in and out of a posture lets my body know that there is, in fact, an escape route and that I will not make it hold too intense a position for too long. It appreciates this, my body:
A chair version is available here .