If I had a dollar for everyone who came to me asking for more core strength, I'd have a lot of dollar bills. Maybe I should have said, "if I had a hundred dollars for everyone... " Anyhoosle, core strength. We all need it, we all want it, well here it is.
Don't confuse core strength with sit ups. Your core is the heart of your being. Your center. It's what holds everything else up and on and in. It's more than just your abs. And come on, you can't isolate one part of your body when everything is connected to everything else! Strengthen your core in order to better your posture, lessen back pain, shoulder and neck pain, knee pain. You getting the drift? A good strong core can help hold that pelvis of yours in the right position, which will positively impact everything connected downwards - legs, knees, ankles, feet - and everything connected upwards - back, shoulders, neck.
Forget six packs (unless they contain beer or flowering annuals), create functional strength that will make your hikes easier, your beach runs more fluid, and your gardening pain free!