Get into a deep lunge position, and place both hands on floor, inside the front leg, arms straight. Top of your back foot flat on the floor, toes pointed behind you. Lean your weight slightly forward, keeping a neutral spine, & feeling a stretch in your hip flexors.
Raise your inside arm, and begin to rotate upward & away from your opposite arm. Keep both arms straight, look up toward toward your elevated hand, exhaling on the way up. Drive your front foot & hand into the floor & don't allow your hips to move. The rotation should come from the thoracic spine (mid/upper back)
Keep rotating, and try to reach so that your arms for a straight line at the top of the motion. Pause & descend with control, repeat for repetitions and then switch sides.