I've been working out with a trainer for a month now. When I came in today, she laughed, clapped her hands and said today is going to be fun. When your trainer sounds like the wicked witch of the west (I mean that very affectionately Jerri) RUN. But no. I went through it. We did things to my abs I didn't know was possible. Angled crunches, regular crunches, supermans, all my arm weights on the bosu stability bubble. May I say OUCH! I knew my abs were going to hurt later. I did not know it would hurt when I breathed.
You need a strong core for whatever kind of exercise you do. I always said I could do it on my own but I haven't. Last month I hired someone to help me, to push me. And she certainly has. She mixes up core and strength training exercises for me 3 days a week. I am working out with her until the end of the year. Then I'll see if it has "taken" enough for me to own it myself.

If you are just beginning a core routine, start out with 3 regular sit ups, 3 angled sit ups on each side and 3 push ups. Build from there. Every little bit helps.