Abs of steel

I've done 4 workouts with intensive ab work in 3 days (with running on top) and it has nearly killed me. However it seems to be doing some good. I had quite a bad back at the weekend which I have recovered from uncharacteristically quickly. My Physio (US: Physical Therapist) in the UK was very keen on core strength from ab work because strong abs support the back.

You may think that with this level of ab workout I now have abs of steel and a washer-board stomach. Sadly, still have the keg version instead of the 6 pack. It must be my age.