This specific warm up is for improved functionality and range in the thoracic spine. I am attempting to keep my feet as forward is possible, screwing them into the ground and illuminating the same torque as a weighted exercise. The back remains neutral, and the pelvis braced as I move slowly through end range. This is best before thoracic extension via squats, deadlifts, or any leg movement that requires proper extension. Try 2 sets of 8-12 reps prior to lifting!