True, these do focus on your abdominal and thus a large part of your core, however I really don't think that these are the most effective exercises that you can be doing.
For the strongest, most balanced core you should consider a different approach.
Have you ever tried doing planks? Not only are they more effective than crunches, they're also safer and easier on your back.
What is a plank? Think of a "plank" or a board as a good reference.
That is how you are going to workout your core.
You are going to keep your body as straight and strong as possible while you place your feet on the floor and elbows on the floor - similar to a push-up but on your elbows instead of your hands.
You don't actually push though, you just "lay" there stiff as a plank.
The core workout I like to do very often About 2-3 times a week I will perform my "easy" core workout by doing to variations of the plank exercises.
First, I do two minutes of the straight, or standard, plank, and then I do one minute on each side of a side plank.
Sounds easy enough, right? It not, believe me.
If you have not done planks before, I think you'll be pretty close to done after your first minute - and that's fine, you should push it.
You'll quickly get a stronger core and be able to do these for even longer.
An advanced core workout Done with the "easy" method, huh? Try this advanced, perhaps, one of the most effective core workouts.
This combination of exercises really gets your core engaged!
- 2 minutes - right side plank
- 2 minutes - left side plank
- Rest 30 seconds
- 2 minutes -regular plank
- Rest 30-60 seconds
- 2 minutes - regular plank with elbows on an exercise ball
Probably, you won't be able to do all of these core exercises your first attempt, but by continuing to work on your core you will be doing this in no time - it really doesn't take long for your midsection to tone up and strengthen up doing these types of workouts.
Just remember, keep your abs engaged and your back straight while doing any of these core exercises.