Here's why:
* Sagittal Plane: This plane divides the body into left and right halves. Movements in this plane are primarily flexion and extension, which are the primary actions of the external obliques. Think of how the external obliques help you bend to the side (lateral flexion) or twist your torso (rotation).
* Frontal Plane: This plane divides the body into front and back halves. Movements in this plane are abduction and adduction (moving away from or toward the midline). While the external obliques can contribute to some adduction movements, their primary role is in the sagittal plane.
* Transverse Plane: This plane divides the body into top and bottom halves. Movements in this plane are primarily rotation. While the external obliques are involved in rotation, it's important to remember that they primarily operate in the sagittal plane.
Important Note: While the external obliques are primarily considered to be in the sagittal plane, their actions can also contribute to movements in the transverse plane. This is because they work together with other muscles to create complex movements.
