It has been discussed for a long time, sit-ups may be the culprit to many of our seasoned exercisers. Heck in the 70's, 80's and 90's, we crunched-we performed hundreds of crunches. We hung from bars and crunched! We placed heavy weights on our chests, behind our neck, and in between our feet...You know what I'm talking about...you know who you are...Even today you want to believe crunches and sit-ups are needed for core strength and definition. Well finally we know that si