Which exercise should I hit to bulk up the abs?

[Mother_Bob]

Well it seems like with the majority of ab exercises, I can do around 20-30 reps before having to stop. What exercise for the abs will allow me to only get around 5-10 reps? I tried the cable kneeling crunch, but it seemed very uncomfortable to perform, along with the cable lying leg-hip raise.

 

[R.Lewis]

weighted leg raises.

There is no point isolating the abs, try more compound exercises like different leg raises and wood choppers

 

[LeiYunFat]

Decline leg raises can be substituted for some weight...but the best abdominal exercise I've found is by far, ab rollouts.

Especially with full arm extension...

All you need is a bar with some weight, so it can roll easily. Start in a dl position, but with your legs straight. Then, keep your feet planted as you roll the rest of your body out, trying to achieve the closest angle to 180 (or zero). Then, use your abs to power your hips back up to the initial position.