Functional Anatomy and Biomechanics of the Core
Domain 1: Functional Anatomy and Biomechanics of the Core
This domain tests whether you can explain how the trunk creates, transfers, and resists force-not just name muscles.
Core as a cylinder
- Local stabilizers: transversus abdominis, multifidus, diaphragm, and pelvic floor. They manage segmental stiffness and pressure.
- Global movers: rectus abdominis, external obliques, erector spinae, and quadratus lumborum. They produce trunk motion and larger moments.
- Thoracolumbar fascia and intra-abdominal pressure create a stiffened cylinder that reduces shear and shares load.
Biomechanics rules
- A muscle's torque depends on force and moment arm; a longer moment arm produces more torque for the same force.
- Compression is not automatically harmful; shear and uncontrolled end-range are often more problematic.
- Anticipatory postural adjustments occur before limb movement; feedforward control precedes feedback.
- Bracing increases stiffness; hollowing emphasizes transversus abdominis. Neither is universally superior.
Worked example
A client lifts a 20 kg box 40 cm from the spine. The load moment is 20 kg × 0.40 m = 8 kg·m, about 78 N·m. Holding the box closer at 25 cm reduces the moment to 5 kg·m. Coaching 'box close, hinge at hips, brace before lift' reduces spinal moment and shear.
Traps
- Equating 'core' with rectus abdominis.
- Claiming a transversus abdominis drawing-in is mandatory for every client.
- Calling global muscles 'bad'; they are essential for load and movement.
- Ignoring breathing and pressure.