Trikonasana - triangle pose.
One foot forward and facing 12 on a clock. The back foot, perhaps a little wider (like our hips), with the foot turned out slightly. This is the foundation. The weight is distributed evenly between the two feet. The low belly, navel is pulled in toward the spine, this creates space in the lumbar and sacral spine. And this is a common challenge to sustain.
The low ribs lift upward, away from the tops of the hips as the upper body leans out over the front leg, the same arm reaching and creating space. When we get as long on that side as we can, we lower the arm. If it only goes to the knee - that's fine. If it gets to the floor, that is no better. Then the torso turns from the navel as the front body turns and the top arm reaches up toward the ceiling.
With each breath, the crown of the head reaches forward, lengthening the spine, and the exhale reaffirms the navel moving into the body and foundation of the feet. Expansion and grounding down.
If there is a strain in the inner groin, a slight bend in the front knee enables better stability and lengthening. Placing the back of the hand on the sacrum enables you to relax the shoulders away from the ears and open through the upper chest and draw the scapulae together on the back. It is important to ensure that the lower portion of the thoracic spine is not arching.
With all this, the spine lengthening and movement of breath, the containment of the pelvic bowl, energy (prana) moving down through the legs and out through the arms and crown of the head. That's the real juice.