Ab rollers are good. Start kneeling then progress to standing. Also hanging knee lifts, leg lifts, and l-sits. L-sit pull-ups are great for time efficiency. T

Ab rollers are good. Start kneeling then progress to standing. Also hanging knee lifts, leg lifts, and l-sits. L-sit pull-ups are great for time efficiency. Those are mainly what I do for core these days, along with some squats/deadlifts, and it seems to be enough to maintain pretty strong abs.