The human body’s intricate movements and structures are often described using a universal language of anatomical planes and axes. These imaginary lines and surfaces provide a consistent framework, enabling clear communication among professionals in fields such as medicine, exercise science, and physical therapy. By precisely defining location and motion, these terms eliminate ambiguity, ensuring that everyone understands exactly which part of the body is being discussed or how a particular movement occurs. This standardized approach is fundamental to accurate assessment, treatment, and training.
What is the Sagittal Plane?
The sagittal plane is an imaginary vertical plane that divides the body into left and right sections. It runs from front to back. While the midsagittal plane specifically divides the body into equal left and right halves, other sagittal planes, known as parasagittal planes, divide it into unequal parts.
Movements that primarily occur within the sagittal plane are typically forward and backward motions. Common examples include flexion, which is the bending of a joint to decrease the angle between body parts, and extension, which involves straightening a joint to increase that angle. Activities like walking, running, performing bicep curls, or squatting all involve significant movement within the sagittal plane.
Understanding Anatomical Axes
An anatomical axis is an imaginary straight line around which a body part rotates or pivots. Each movement in the body occurs around a specific axis, which is always perpendicular to the plane in which the movement takes place. There are three primary anatomical axes that correspond to the three main anatomical planes.
The transverse axis, also known as the mediolateral axis or frontal axis, runs horizontally from side to side, essentially piercing the body from left to right. The anteroposterior axis, or sagittal axis, runs horizontally from front to back. Lastly, the longitudinal axis, also referred to as the vertical axis, runs vertically from the top of the head to the feet.
The Sagittal Plane’s Associated Axis
Movements performed within the sagittal plane consistently rotate around the transverse axis. Therefore, for movements that occur in the sagittal plane, which divides the body into left and right, the axis of rotation must run horizontally from side to side. For instance, during a bicep curl, the forearm flexes and extends in the sagittal plane, and this motion occurs around an imaginary transverse axis passing through the elbow joint. Similarly, when performing a squat, the hips, knees, and ankles undergo flexion and extension in the sagittal plane, rotating around their respective transverse axes.