Our upright posture is largely determined by the balance of muscles known as flexors and extensors. A flexor is a muscle that draws two parts of the body closer to one another. Lifting your knee up to the chest is flexing the leg. When you walk and that same leg moves behind you it is the extension of that leg.
We can look at the front of the body being the flexors. Muscles that fall into the category are the quadriceps (not mainly a flexor but involved in the action), the psoas, the rectus abdominus (sit ups muscle). The back of the body are the extensors- gluteus maximus, hamstrings, erector spinea (spinal muscles that run up the back). This doesn’t mean that flexors can’t extend—they can and do. It is just that they have a primary purpose which is what we are looking in this post.
In the picture on the left we see a body that lives in a balance of flexion and extension. The front of the body is matched in length by the back of the body. The lower belly and the lower back are equally long. You can see the same relationship in the legs—the hamstrings and quadriceps live in harmony balancing each other nicely.
When we move to the picture on the right things get ugly. Not only do we have a body with poor posture but the relationship between the flexors and extensors has been thrown completely out of balance. Because of the nature of this bad posture, which is a very common pattern that I see in an overwhelming number of my clients, the flexors at the front of the body have become distended and are actually overly long with the appearance of extension. When the thighs lean forward of the pelvis, the quadriceps become over stretched (and they tighten full of tension as well), the rectus abdominis becomes overly long allowing the rib cage to lift too much in the front. At the back we have chronically shortened calves, hamstrings, erector spinea and quadratus lumborum to name a few.
To put it simply we have basically turned out flexors into extensors and vice versa. The balance of the flexion and extension is essential to achieving good posture and movement patterns. The essence of my work is to try and move people from being the picture on the right to becoming the picture on the left.