Here are some of my favorite core exercises. These exercises are great for people retuning to working out after a hiatus or if you are simply looking to mix things up. I have struggled with 'back problems' for about 15 years. After 4 surgeries, several rounds of injections and many rounds of physical therapy, I have learned that variations and appropriate progressions are key. It is not acceptable to avoid ab work because of back pain. If you are working with a physical therapist, ask them for core homework. The goal is to continue strengthening the problems areas of the core and mitigate future pain. As you work on this critical goal, you must strengthen all sections of the core. For me, it has been a lot of trial and error. With the assistance of great physical therapists, I have been able to create a challenging core workout. Below is a list of my favorite exercises. I think starting with timed intervals is better than reps. If you are just starting out begin with 20 seconds of each exercise. Do not forget to account for doing the right and left side on the side-lying exercises - there this routine will take between 7-9 minutes.
Plank Variations - All Sections
Plank Barrel Roll
Side Body Specific
Side-Lying Leg Lifts to Crunch
Supine Options- All Sections