Core and abdominal training is great, but seriously, it’s not all that important.
Back in the day, core training was all the rage and everything that was supposedly “functional” was about working the core.
Then it was about the hips, then the legs and so on.
The lesson I eventually learned was that there is no part of human body that’s more or less important than any others.
I just talked to a guy who broke his pinky toe and he was saying how it had thrown his entire gait and back out of kilter. So maybe we should develop a whole pinky toe program. Books! Videos! Entire classes at the gym should be devoted to nothing but pinky toe health and fitness!
I know it sounds crazy, but why should a “core” class or arm workout make any more sense? Those muscles are important, but I would argue they are no more linked to your health, performance or appearance than your toes.
Calisthenics has the advantage of requiring all of your muscles to become conditioned. If you want stronger legs you can’t just plop more weight on a machine and ask your muscles to work harder. NO! Advanced leg training requires more than just extra quad strength. It demands stability in the hips, control of the hamstrings and a technicians touch with even the muscles in your feet.
So don’t emphasize anything, and don’t neglect anything either. The best way to ensure your “problem areas” are getting in the best shape possible is to make sure everything else is also getting it’s share.