FROM MY PT SCHOOL NOTES · FABIO · CHAPTER 16
How Does the Lumbar Spine Share Load During Movement?
The lumbar spine transfers load while permitting movement through discs, facets, muscles and ligaments.
Recognize the tissues doing different jobs
The lumbar lecture covers large vertebral bodies, intervertebral discs, facet joints and ligamentous and muscular support. Different tissues resist or accommodate compression, shear, bending and rotation.
The familiar lordotic curve varies between people and across tasks; the global line of gravity is not a fixed personal ‘correct posture’.
Describe motion and load
Lumbar flexion, extension, side bending and rotation are distributed across segments. The disc and facet behavior changes with geometry, force and duration.
The original notes use viscoelastic and loading models. They are helpful teaching simplifications, not evidence that one amount of flexion universally damages a disc.
Connect the spine to a useful activity
Compare reaching sideways, lifting an object from a shelf and sitting for a prolonged period. These involve different external moment arms, muscular demands and recovery opportunities.
The evaluation must still address symptoms, capacity and function. A force diagram alone cannot diagnose disc pathology.
Check your reasoning: Does visible lumbar flexion during a task prove a disc is injured?
No. One posture does not independently identify pathology or predict injury.
Try the mechanics on a real task
Example: Two people lift the same 8 kg object. One holds it near the trunk; the other reaches forward to place it on a shelf.
Work through the reasoning
Answer: The object has similar gravitational weight, but horizontal/perpendicular moment arms about relevant joints differ. External moments and muscular demands can change; neither method alone proves injury risk for one person.
Common trap: Declaring a universal ‘safe posture’ from one simplified spine diagram. Remember: Describe load, position, speed, task and individual capacity together.
Source: my original FABIO Lumbar Spine.pdf material, summarized as a free conceptual lesson. No third-party diagrams reproduced; this is not a patient-specific clinical protocol.
