The front Heel shouldnt be involved in the manouver, the front Heel is the Biomechanical Break. The Balance of the manouver are the Knees The Heel locks the Adductors stopping the Abductors from working . Thats what causes leaning with the shots, and loss of oral stability and balance. Usually caused with the feet being to wide, and compensating, making the shoulders tighten and slowing down speed of delivery.