The exercises listed here will give you a bigger bang for your buck than crunches, since you’ll be working not just your core but other muscle groups as well. Here are my favorites:
1)Ab wheel or ball rollouts-This is probably my favorite abdominal exercise, and it always gets me sore! Make sure to keep your abs tight, rib cage down, and hips slightly tucked under.
2)Hanging leg raises- I’d have to say that these are my least favorite(because they are hard!) but one of the most effective. If you do them from a bar, you get the added benefit of working your grip and upper back at the same time, but they are extremely challenging. I try to bring my toes all the way up to the bar without swinging. If you can’t do that, you can just hang from the bar and tuck your knees up as far as you can, or use the machine most gyms have to support your arms. Make sure that when doing this you aren’t just raising your legs up, otherwise you’re just working your hip flexors. You want to actually curl your hips up, like you’re trying to bring your belly button and ribcage together.
3)Farmer’s walks and overhead carries- Carrying heavy dumbbells at your sides or holding a dumbbell overhead really forces your abs to work. I like to do these as finishers to an upper or lower body workout. You can even try doing them off-set, with two different weights in each hand to challenge the core even more. They are a great grip and upper back exercise as well.
5)L-sit holds and modified front levers-It has been a goal of mine to one day be able to do a front lever. For now, I just do a modified version with knees tucked in, but even that is a super challenging core, grip and lat exercise. SO much harder than it looks! L-sits are another great core exercise to incorporate into your workouts. I do a few sets of L-sits or front levers at the end of a workout or between exercises for a 10-15 second hold. You will feel the burn!
6)TRX or exercise ball pikes- In a pushup position with your feet in TRX straps or on an exercise ball, use your abs to bring your hips up towards the ceiling with your legs straight until your hips are over your shoulders. If this is too challenging, you can just tuck your knees in to your chest.
I don’t do them much myself, but you can also do planks and all the variations of planks there are, as well as Pallof presses. And don’t forget that just heavy lifting in general works your core as well. I don’t necessarily think crunches are horrible, but you do NOT have to do them to get great abs.