The Spine is an S Shaped Spring as a result of standing and walking erect. The Balance required for a Bipedal to walk is impressive. Along with the Spinal Groups, the Spring in our Step involves constant Muscle triggers along a vast network in the Pelvis, Thigh and Calf. These Muscles are the largest in the body and play a key role in Balance and therefore Posture for the Human Structure.
With time, these Muscles can lose their full extension and Contract causing the Pelvis to rotate out of Neutral Posture producing a cascade effect for the Spine as it tries to compensate thus Degrading the S Shape Curvature. Regular Stretching for the Glute, Hamstring and Calf is a good way to reset the Muscles toward a state of Full Extension and Limber, Neutral Posture.