Which of the following is a 'global' stabilising muscle of the spine?

The external oblique is correctly identified as a global stabilizing muscle of the spine. Global stabilizers are primarily responsible for supporting the spine during movement and are engaged during dynamic activities. The external oblique works in conjunction with other muscles to stabilize the body's trunk and maintain posture during various movements.

This muscle plays a significant role in trunk rotation and lateral flexion, which are essential for functional movements in everyday activities and sports. By working to stabilize the pelvis and spine, it assists in maintaining proper spinal alignment, thereby reducing strain on the spine during movement.

In contrast, the transverse abdominis is considered more of a local stabilizer, responsible for providing core stability and compressing the abdominal cavity to support the spine. The multifidus also serves a stabilizing role but is classified similarly to the transverse abdominis, focusing more on local stabilization. The pelvic floor muscles also contribute to core stability but are not classified as global stabilizers.