Which axis is involved in trunk extension from a flexed position?

In trunk extension from a flexed position, the primary axis of movement is the Y axis. The Y axis typically represents the sagittal plane in human biomechanics, which is the plane that divides the body into left and right halves. Trunk extension occurs as the spine moves from a flexed position (bent forward) to an extended position (upright), involving primarily motion in this sagittal plane.

When performing this movement, the vertebral column pivots around the Y axis, allowing for effective extension. This motion is fundamental in many activities, such as standing up from a sitting position or returning to a neutral standing posture after bending forward.

Understanding the role of the Y axis in trunk extension is crucial, as it helps to clarify how the sagittal plane governs movements related to flexion and extension, which are essential concepts in clinical biomechanics.