Planks are one of the best core exercises. Everyone wants to do fancy sit ups, but there is no need to over complicate things.
This is a plank series I like to incorporate into my workouts. If you can’t do all of these movements, then start off simply and incorporate the more complex as you go along. Remember you don’t’ have to do the hardest movement around in order to get better and more functional. All you need to do is find the movement that challenges you enough to get a sufficient dose to change.
When holding the elbow plank keep constant tension throughout your body. When doing plank taps extend one arm out at a time keeping the same body position throughout the movement. When doing the ring plank have your hands on the rings and your feet on a box to keep them the same height. With a single arm single leg ring plank, you will have one are on the ring and the other arm off the ground floating. The opposite leg will be on the ground while the other leg is floating. Ring body saw you will be on your forearms and your feet will be in the rings. Slide your body forward and back making sure you butt does not raise.
Have fun trying these movements and make sure you can do all with perfect form before you progress.