Pictured here is a variation of the extended side angle. In the traditional pose, the front forearm rests lightly on the front thigh. Another version is to bring the front fingertips to the floor, behind the bent leg. For a core-strengthener modification, raise the front arm, parallel to the floor, as indicated in this image.
In any of the variations, try to open the chest, stacking the shoulders, and push into the outside of the back foot. Seek a perfect diagonal from bottom leg to the fingers of the top arm, both of which should be lengthened to the max. When the pose is held for a minute or too, you should feel it in the quads of your front leg.
“It is through the alignment of the body that I discovered the alignment of my mind, self, and intelligence,” said B.K.S. Iyengar in his epic “Light on Life.”
Iyengar said about poses like this, “Stretch every part of the body, concentrating on the back portion of the whole body, specially the spine. Stretch the spine until all the vertebrae and ribs move and there is a feeling that even the skin is being stretched and pulled.”
While Iyengar wrote this many years ago, the need for this pose has only increased, as many of us have bad habits that affect our posture, negatively.
Just like with any other new diet or work out plan, consult a yoga therapist to determine what is best suited for your particular physical and emotional wellbeing.