I was doing this pose in class last evening. It has a very expansive feel to it. You need to pull in to yourself strongly and hold your standing leg very firmly, but the expansion comes through extending your spine upward to be the tallest you possible and allowing the leg to reach out away from your body, away from your centre. This is like life; once we know our core beliefs, our true selves, we can reach out away from that core while maintaining our strength, maintaining our truth.
To take Utthita Hasta Padangustasana, start by standing in tadasana or mountain pose- simply standing tall with feet together, hands at the sides. Pull the knee in to the chest to begin. Pull into your core by lifting up at the pelvic floor and pulling the abdominal muscles in and up just below the navel. Keeping your standing leg firm, bring your gaze to a point on the wall that isn’t moving to help you maintain your balance. Draw your arm inside your knee and then hold either the big toe or the outside the foot. You can stay right here or you can start to extend the leg to wherever is comfortable for you. Ensure that the shoulder blades stay planted firmly on the back and that you extend the spine upward. Tuck the tailbone toward the heels slightly and hold your abs and pelvic floor toward centre.
A variation is to simply hold knee to chest as shown here: