Specifically-speaking, with regards to how it will benefit your powerlifting or Olympic-lifting numbers.
Also, specifically-speaking, just the abs and obliques. Let’s exclude lower-back since squats and deadlifts will surely already develop it without doing any silly lower-back specific exercises.
In about two-months from now I’ll start lifting weights again. I wanna know if it’s necessary for me to include direct core exercises or just assume that the kind of movements that I have in my program will already (albeit indirectly) engage my abs and obliques enough.
2-3 times a week, I do ab wheel roll-outs and a few planks holds with the ab wheel. I find this does all I need core wise. I used to more do variety, but I haven’t found it to be necessary for me.
I have all kinds of issues if I don’t train them regularly though.
I hurt me back being stupid and core activation is now part of every one of my workouts. That said I’ve seen opinions from various parties in the know citing EMGs, anecdote and more that “big” movements train the core musculature well if you practice good movement and bracing mechanics so direct core training might not be bang for your buck. Be cautious though Squats and deads alone may have plenty fo stabilisation requirements along one plane but may lack in others. Fill in the gaps I guess with other movements.
If you need to develop those good bracing patterns and core activation/stability or have a history of injury like me then direct core training is useful
My lower back gets a lot more out of back extensions than squats and deadlifts. I know some opinions say those big movements are all there is to it, but, in my personal experience, the weak link needs direct work. My weak link is nearly always my lower back, so it needs direct work.
As somewhat of an aside, I think this opinion comes, in part, from getting a low back pump when you do these movements. Then we say “great - my low back got pumped, so it got worked.” In reality, maybe we should think “my low back got pumped, and I don’t want it to be the primary mover, maybe I should fix it.”
I know your question was more around the ab side, but that just stuck out to me. I think we should do abs too.
My core feels strong, until I actually perform a core excersise. I run a pretty standard Bench/Squat/OHP/Deadlift routine, with plenty of barbell abuse, and my core is still relatively weak.
I would absolutely include core work.
I tend to just add a set at the end of every barbell movement. It doesnt add much time, it’s not as boring as running straight sets of core, and it usually positively impacts my max effort lift for the day.