I really never put enough of a priority on having a strong core. I would rather run than anything and doing sit ups gives me hives. At one point I had a very strong core because I was cross training and swimming and running. This was just before my first half marathon which I finished in 2:02 and change. After that race I cut down on all my workouts and stuck to running only. I gained back 20 of the 50 lbs that I had lost which wasn’t all fat but it wasn’t all muscle either. My pace slowed down and I got lazy. It showed in how tired i was after a run, how slow I became (pushing 10 minute mile from 9) and how snug my clothes became. Recently I finally managed to work Tabata workouts into my running routine. I’ve worked arms, abs and butt. it’s only been 3 weeks but I now see it in my run stats. I am running faster without running harder. I thought that might be from running more but it is most assuredly from doing my core work and now I’m obsessed with a six pack again. I’ll take a 4 pack but getting a core of steel as much as I can at 47 is my goal. Sometimes you need to see it for yourself to understand it and believe it. Whatever it is, go get it and do whatever it takes to get there. You can do it!