Do you find yourself doing countless crunches, without seeing any visible results, while also developing a serious neck ache? Or maybe you're the stud with an 8 pack, who can barely hold a plank for more than 20 seconds without shaking vigorously?
If you fall into any of the categories mentioned above, then take a look at my dumbbell walkout exercise (via MensHealth). They're numerous progressions that can be implemented into the walkout, but the primary sequence can be used to develop flexibility, as well as building a solid core.
Start implementing this movement consistently in your regimen and you're guaranteed to see results.