What “core strength” actually means

It is not your abdominals, and it is definitely not how long you can hold a plank.

The core is the whole cylinder — front, back, floor, and the breath moving through the middle of it. Most people who tell me they have a weak core actually have a well-developed front and a back that has stopped participating. Holding a longer plank will not fix that. It will just make the strong parts stronger and the quiet parts quieter.

In class I would rather give you thirty seconds of something you can barely coordinate than two minutes of something you can already do. Coordination first, then load. That order is the whole method.