यह brace pattern

Holding the trunk still while something tries to bend, extend or twist it. Planks, dead bugs, Pallof presses and ab-wheel rollouts all belong here. This is what the trunk actually does under a heavy bar, which is why anti-movement work transfers better than endless crunches.

Across the 44 brace exercises on this site, the prime movers are the abs, obliques, lower back, adductors, hip flexors. Which one leads depends on the angle and the equipment, not on the pattern alone.

Twice a week is a sensible default for every pattern. A programme built on movement patterns rather than muscles is harder to leave holes in — if every week contains a push, a pull, a squat, a hinge, a carry and some trunk work, very little gets missed.