What's the best ab exercise?
My workout buddy and I are always looking for ways to change up things. When working abs, we use the ab machine, stability ball, and incline bench. These are getting too easy for me and she's not feeling the burn like I am, but I can't explain to her how to tighten her core. I can feel the burn in the upper part, but need some advice on how to feel the burn lower. I know it's one muscle, but how do I make the burn feel all over?