CENTERLINE PRINCIPLE

UNDERSTANDING THE CENTERLINE

A fundamental knowledge of human anatomy is the key to any profound understanding of the centerline principle. First, we must understand the human body is three dimensional. In geometry, these dimensions are height, length, and width. In physics, any specific location in three dimensional space is ploted on an X-axis, a Y-axis, and a Z-axis. In human anatomy, these dimensions are designated as the coronal plane, sagittal plane, and transverse plane.

The centerline is located at the intersections of the coronal plane (X-axis/height) and sagittal plane (Y-axis/length). This line of intersection is designated as craniocaudal axis along the transverse plane (Z-axis/width). This craniocaudal axis is the centerline. It is imperative to understand this centerline runs through the human body internally. It precise location is represented by the plumb line hanging from each of the hooks in this chart of the human skeletal system.

ANATOMICAL CENTER OF GRAVITY

The precise point of xia dantian is located on
the craniocaudal axis at the intersection of
the coronal plane (X-axis/height), the 
sagittal plane (Y-axis/length), and the
transverse plane (Z-axis/width).

Study the chart above carefully. Take special notice of our anatomical center of gravity. It is located near the center of the pelvis just above the point at which the femur joins to the pelvis. This anatomical center of gravity is designated as "xia dantian" (下 丹田) in Classical Chinese Martial Arts. The precise point of the xia dantian is located on the craniocaudal axis at the intersection of the coronal plane (X-axis/height), the sagittal plane (Y-axis/length), and the transverse plane (Z-axis/width).

The gravitational force of the earth is constantly pulling on this central point, which is located on the centerline. If we stand perfectly straight, gravity enters the body on this centerline through the perineum approximately two inches behind the scrotum and approximately two inches in front of the anus. Typically, gravity travels along the centerline through the abdomen and thorax until it exits the body at C7 (the seventh cervical vertebra). Depending on the position of our cranium in relation to C7, this line of gravity may or may not re-enter near the base of the skull and exit near the apex of the skull.

A cursory study of the chart above does not seem to illustrate this fact very clearly. However, it is noted on the chart. This is because, in a more relaxed and natural position, the vertebral column is more severely curved than represented in the chart above. In reality, humans tend to stand in a more natural and relaxed position. Humans almost never stand completely straight.

PROPER BALANCE

The only way we can maintain perfect balance is to properly align C7, the xia dantian, and the center of our heel (slightly behind the ankle joint). These three points must be positioned directly on the centerline of the coronal plane. This proper alignment produces natural equilibrium. Such alignment correctly uses the structural framework of the human skeletal system to balance the force created by the pressure of gravity pulling on our body mass. A profound understanding of this is the secret to establishing and maintaining proper physical structure and balance.

CONCLUSION

With a profound understanding concerning this fundamental principle of the centerline, how it relates to proper physical structure, gravity, and balance, we can proceed toward learning how to physically implement anatomically correct alignment of an arched vertebral bridge in relation to the centerline. However before we explore the application of a new skill, it would be wise to address the difficulty of learning a new skill and overcoming such diffuculty.