What does core training actually do?

Less than the fitness industry claims and more than the sceptics allow — the core's main job is resisting movement, not producing it, which means most traditional core exercises train it in the wrong way.

What "the core" means. Not the abdominals alone. It includes the deep abdominal muscles, the obliques, the muscles along the spine, the diaphragm above and the pelvic floor below — functioning as a pressurised cylinder that stabilises the trunk.

What it actually does. It transfers force between upper and lower body and resists unwanted movement: resisting extension, flexion, side bending and rotation while the limbs work. A heavy carry, a squat and a press all demand core work without any dedicated exercise.

What the evidence supports:

Anti-movement exercises — planks, side planks, carries, dead bugs, Pallof presses — which train the actual function.

Heavy compound lifting, which trains the core substantially, meaning a separate core session is frequently unnecessary for people who squat, deadlift and carry.

Core training for low back pain, which helps — though evidence suggests general exercise helps roughly as much, so the specific programme matters less than doing something.

What is overstated:

Endless crunches and sit-ups, which train spinal flexion repeatedly — a movement some spine researchers consider best limited — and do not reflect how the trunk is used.

Core work for visible abdominals, which is determined by body fat, not by abdominal training. You cannot reduce fat from a specific area by exercising the muscle beneath it.

"Activating" deep muscles through specific drawing-in techniques, which was influential and has not held up well; most people's deep muscles work fine without conscious recruitment.

Core work as injury prevention, where evidence is mixed and weaker than commonly claimed.

The practical position: include anti-movement work a couple of times a week, prioritise loaded compound movements, and treat any claim that core training will flatten a stomach with scepticism.

General information, not medical advice.