 Any attempt of the shooter to create a dynamic motion of the sights (muscle the sights onto the target vs. allowing the posture to aim) will result in a jerky posture where the sights do not sit still on the target.For the shooter to maintain accuracy, the muscles cannot exert force on the rifle, and the skeleton must be aligned to set the rifle (and therefore the sights) onto the target.The core, while resting on the ground and relatively far away from the rifle, is nevertheless aligning the spine and pelvis to which the shoulder and arms and neck are connected.