Having A Full Workout Just For Abs
All you need is 15 minutes. If you’re already doing compound exercises like squats and deadlifts, one or two ab exercises for 2-3 sets each at the end of your workout is sufficient.
Only Doing Crunches
I heard the question you just screamed “So what’s better than a crunch, maaan?” There are dozens of exercises that are much more effective than the traditional crunch.
In fact, the traditional crunch is one of the least effective ab exercises you can do. And just because you can’t perform these other movements for hundreds of reps doesn’t mean they’re not effective.
Only Working In One Angle
Your obliques, transversus abdominis, rectus abdominis, and erector spinae are all part of your core, but they’re different muscles with fibers running in all manner of directions. You must train them in more than just one angle.
Complex, difficult movements like windshield wipers can work the whole team at the same time, but if you’re not there yet, don’t take it as an excuse to revert back to middle-school-crunch tests.