In natural human postures, the spinal column should form a line with very light undulations, but usually in most men convexity more or less marked in their backs can be found on the upper area of the spine (chyphosis).
Once you expanded the movement of the spine with exercises of straightening, you should practice the following exercise, which makes your spine more flexible and dynamic, and that at the same time is the synthesis of every natural movement of the spine.
First, the three main postures shall be considered since at every moment we are assuming one of them, that is, the standing, seated and lying down posture. We got so much used to pass from one to another posture, or to remain for hours in certain posture, that we have lost any critical sense to notice if our present posture is correct or not.