This asana is a very STRONG POSE.

Various WORKING MUSCLES: 
The arms,
Spine,
The Standing Leg,
and the Lifted Leg are all working very hard.


The LENGTHENING  aspect is also very important:
Arms
Spine
Standing Leg
Lifted Leg

SCAPULA MOBILITY is extremely important allowing the arm to position itself without over-mobilizing the glenohumeral joint and for mobility in the thoracic spine.

Allow the deeper, more intrinsic back muscles to do the action of spinal extension. 

Bring your awareness at all times to the legs remaining adducted and internally rotated in this pose.    We often think that more extension is better will automatically open the hip externally and will risk over-mobilizing the sacroiliac joint and overworking the lumbar spine to achieve that height of the leg.

  Focus more on your breath.  Stay quiet and calm with it.. The longer the pose is held, the deeper the body craves for breathe.  Be mindful not to lose those stabilizing actions to prevent injury to the spine and shoulders.