I can’t find an answer in any of my anatomy or yoga books, so I’m hoping someone here knows the answer. Although in Utthita Hasta Padangustasana you hold the big toe, I’ve decided I’d like to develop the ability to let go of my toe and hold the pose briefly with my leg out in front of me. However, my leg immediately falls to about a 45 degree angle. Other than simply continuing to practice this pose, does anyone know what muscles are being worked, or what other poses might be helpful? Is it abs? Quads?
JR,
I love these posts. It really challenges me. As a yoga teacher and frequent contributor here I feel compelled to ask why you’d want to do such a thing (purpose other than your own craving), and to warn that the pose you mention places a lot of torque (strain/demand) on the sacrum and sacroiliac joint (not to mention the lower back in general).
And at the same time I am feeling this pull, I realize you’ve not asked for that. You merely want to know which thingies do the lifting and holding of the thigh bone. The answer to that is the hip flexors of which there are three; iliacus, psoas, and rectus femoris.
Thank you, InnerAthlete. And thank you also for the warning about the sacrum and sacroiliac joint, too. (Perhaps that is why there is no “Extended Leg Balance Pose”?) My thought was just that this was one part of my body that was out of balance, not sufficiently toned. I know it is not a flexibility issue, so I was wondering what needed extra attention. Perhaps . . . nothing that is not already being addressed in its proper place?
Personally JR I find the constant human chatter about “core” muscles to be quite ridiculous. Core muscles keep human beings standing erect all day long. The last thing most bipeds need is additional work on the iliopsoas. For most, that muscle is already short, tight, and subject to spasm.
The pose is as it is for reasons 
I advise doing the same pose in the supine position (on your back).
Bear in mind that the three alignments are: down leg straight, up leg straight, holding arm straight. If this is not possible then you are most served by using a yoga belt for the holding.
gordon
just to add to IA,s excellent contributions ,this pose is in the ashtanga primary series as taught by pathabi jois.
Tried to put link to picture of pose but am not allowed but ,they call it uthita hasta padungusthasana B
I would be careful practicing this, (as with all postures) for the reasons given by IA . note it comes at the end of all the standing poses in the primary series for a reason,pay particular attention to the standing leg ,and working the back of the legs,as we all tend to overwork the quads and under work the back of legs.you can perhaps work with raised leg bent or practice with a belt but learning to not use the strength of arm to hold leg up if you get what i mean, keep awareness of sacrum ,dont let tailbone fly up.I cant imagine its a particuarly important pose,navasana would give us some clues to how to work, oh and dont lift the straight leg higher than eye level ha ha good luck
I agree that you must be careful when keeping the leg lifted while letting it go in Utthita Hasta Padangustasana, but I also see it being a great way to strengthen the hip flexors, as long as you have stability through the pelvis. The only way to create stability in the pelvis and lower back is by using the muscles that are designed for this (for endurance), such as the pelvic floor, obliques and transversus abdominus.
What you don’t want to do is allow the lower back to arch and the hips to tilt. This can take tremendous core strength, so you will likely have to work up to it with easier exercises the you can have stability in.