I'm curious about what kind of programs people are doing for their core workouts. I've been going to the gym since August for upper body workouts, alternating triceps/back and biceps/pecs for a total of four days a week. All my workouts incorporate core training, and I definitely can see improvement in my abs, but I'm wondering about whether I'm doing the right set of exercises at the right level of intensity. I'm generally pretty fit (at my ideal weight) and 45 years old. So here's what I do:

--crunches with my feet on a ball: 20 reps x 4 sets
--planks: 45 seconds x 3 sets (with cobras in between sets)
--bent leg lifts in the captain's chair: 15 reps x 4 sests
--back lifts (those things that make one look like a ship's figurehead): 15 reps x 2 sets, with a 5 lb weight
--side sit-ups for my obliques (on the same support as the back lifts): 12 reps x 2 sets per side, with a 5 lb weight

Question on the planks: I hold the position quite flat, but in the mirror I look like I'm hunching my shoulders a bit, and I feel stress in my lower back. Is that normal for the position?

So, what do you think? And what's your core program?