When it comes to the health of the human body, there are many factors that can be measured. Levels of these factors can be considered Normal or Abnormal. For instance, Glucose levels, Cholesterol levels, Visual acuity, Blood pressure, and Body temperature are some of those measures that have clearly defined normal limits that most of us are familiar with.
From an Alignment Perspective (with consideration of the front and back view) a person with Normal Structure will visually appear to be symmetrical--the head, shoulders, hips, and arms will all be even. There will be no sign of a shift or rotation to either side. From this view, you should be able to draw a vertical line up, from directly between the feet, up towards the bridge of the nose. Passing along the way (as we move upward) the center of the pubic bone (pubic symphysis), the bellybutton (umbilicus), and the notch above the sternum (manubrium). In addition, if you were to take an x-ray of someone with Normal Structure from the back, you will see the spinal column (made up of separate vertebrae and vertebral discs) will be centered on a similar straight, symmetric line.
From the side view, in a Normal Structural alignment, there are some anatomical landmarks that should line up with a vertical line that starts (at the bottom of the body) at the bump on the outside of your ankle (lateral malleolus). These points, as we move upward, are the Protuberance on the side of the hip (greater trochanter), the tip of the shoulder (acromion), and the outside hole in the ear (External auditory meatus). When looking at an x-ray of someone with Normal Structure from the side, you will find that there is a well-defined neck (cervical) curve that curves forwards, a mid-back (thoracic) curve that curves backwards, and a low back (lumbar) curve that curves forwards.
When there is Normal Structure, the body is in an advantageous biomechanical state. Consequently, when body shifts or rotates into an abnormal structural position, it can lead to a poor biomechanical state leading to Conditions such as:Anterior Head Syndrome (AHS) and other Structural conditions upon which we focus.