In case you haven’t heard, crunches and sit-ups are overrated. The best way to build the six-pack of your dreams is almost never to do rep after laborious sit-up rep.
The key with the Pallof is to spend plenty of time with your arms extended. When you draw your arms close to your body, you’re taking tension off your core and “resting,” so work to keep those momentary breathers at a minimum. And when you extend, do so deliberately, establish a strong, sturdy position, and hold steady for a few seconds.
The standing Pallof is the easiest version, so once you master that, step things up. Tall kneeling Pallofs will challenge you more, forcing you to fire more aggressively with your glutes. Once you can do 3 sets of 8 to 10 reps with those, progress to half-kneeling Pallofs, kneeling on the knee closest to your cable. Make sure to externally rotate your outer hip, and keep working to stay steady.
Whatever you do aim for 3 sets of 8 to 10 reps. You can build them into your routine every day. Your core should be tight all the time, and no move will tighten it up quite like this one.
Source: How to Get a Six-Pack Without Doing a Single Sit-Up