When attempting the posture, it might be useful to break down the movement into two distinct segments: the arm balance work and the core strength movement. If you want to work on the core strength and the legs in the posture start off in a seated position. Then hook your right thigh around the back of your right upper arm. After that, think about pulling the head of the right thigh bone into the hip socket while straightening the leg. Be sure your right hand is pressed firmly into the ground near the pelvis and that you keep your right leg as close to your torso as possible. Next, draw the lower ribs into the body while sucking in the lower belly and activating the pelvic floor. After practicing on the left side, try it with both legs.
Remember that it takes more than just brute power to lift your body off the ground. Strength in yoga is a careful articulation of grace and flow.