One: the short answer: yes, focusing on the core, i.e. being fully stable in the whole cylinders of your legs and not just bracing into the outside, or falling to the inside, is a really awesome skill to develop. As a whole in this culture, we tend to be quadricep and some-hip-flexor heavy in our movements, and re-training the hamstrings and glutes (we could do well to know these as part of the core) to work in harmony is a really good idea for probably 99% of us.

Two: the longer answer, and context (all in my humble opinion, of course): We have a huge amount of movement available to us as human bodies. Almost all of us, to varying degrees fall into different kinds of movement “trances,” another way of saying we have some movements that are easy/intuitive to us and some that seem very perplexing and difficult if not impossible. This applies both to macro (any overt movement you can see, i.e. more complex, multi-joint movements like a tennis serve, or chopping vegetables, or a leg press) and micro (an isolated portion of some of the gajillions of little things that happen in an immensely complex sequence to do really any macro-movement). It actually applies much more to the micro. And it’s coordinating those micro-movements that we tend to lose sight of, or rather feel of, because we can fall into that trance quite a bit and still get the macro-movement job done. Eventually, it catches up. We call that someone’s core being “weak.” It’s those smaller, often stabilizing, movements that we think of as core movements (and the ability to do them well, i.e. feel and recognize a significant chunk of your internal body map.) We tend to call that “core strength.”

And so … in my eyes, it’s really important less that we do any exercise a particular way, but that we are ABLE to do any exercise a variety of ways. Bonus points that we can really feel the whole experience in our bodies while it’s happening. (Which is really the point, no? That’s transference, i.e. functional fitness, in a nutshell. Most of us don’t bench press to get good at bench pressing; we do it because it makes us feel good, functionally stronger in our daily lives, the mental focus, etc.)

Which brings us back to the short answer. The trance tends to be moving the legs with the quads and stiffened psoas type motions. Breaking the trance involves using our deep back stability, i.e. hams and glutes as far as the legs go.

Thanks for asking  Hope this helps! L