I spent some time this weekend looking into the issue of core training (training the abdominal and posture muscles). Unfortunately, I had to cut through a mountain of nonsense to get to any real information. You would think training the core would be relatively simple, but I found that trainers are prescribing all sorts of complex moves.
My other motivation was to tie in natural hunter-gatherer movements with core training. In the modern world, many people often have weak core muscles due to prolonged sitting. However, I feel that hunter-gatherers must have performed certain movements that naturally strengthened the core. It's probable that these moves are missing from modern fitness routines.
It seems that specific moves used to train the core are separated out from a natural whole movement. For example, the "bird dog" move is often prescribed to strengthen the lower back:
What does this look like to me? Part of a crawling movement. I have seen my toddler stop crawling partway many times and end up in a similar position to this. Also, if you rotate the image 90 degress, it also looks like somone climbing upwards (like rock climbing).
Another movement that is prescribed is the plank:
To me, this looks like part of quadrupedal movement. The plank has a person resting on their forearms, but resting on the hands would have the same effect.
Finally, a move that isn't often prescribed for the core (but should be) is the farmer's walk:
A new study by Stuart McGill shows that moves in strongman competition like the farmer's walk strengthen the core. And clearly, the farmer's walk was a move performed by hunter-gatherers. I'd bet that the weight was occasionally lifted overhead as well, providing more challenge for the core muscles.
If you put this all together, you have a routine of primal movements that can strengthen the core:
Quadrupedal movement (on hands and feet)
Walking while carrying weight (farmer's walk)
Walking while carrying weight overhead
Interestingly, these moves are likely to be covered in MovNat training. I feel that a series of natural movement such as these should be sufficient to train the core muscles. Of course, a person can start with poses such as the plank and the bird dog to initially strengthen the core before integrating them into the whole movements.