
But the worst part of sit-ups isn't what they're missing, it's what they're acting on — namely, the spine. Imagine that you're standing up, and throwing your torso forward to touch your toes, over and over. It's easy to see the havoc that wreaks on the lower back, and it's similar to what's happening with most sit-ups. While performing a slow and controlled sit-up can work fine to build one section of your abs, there are far superior alternatives that can target the entire core, while strengthening other parts of your body and even burning fat.