So many articles, some of which were written by me for this very site, deal with chasing the coveted six-pack, the apparent standard of beach season beauty. That's all well and good, but let's not forget the core (pun intended) reason for working out: to strengthen our bodies, to physically challenge ourselves. When people say, "I work out to lose weight," I always ask, "What happens after you've lost the weight?" Exercising is a lifelong commitment and not just a bikini-body prep. With that in mind, let's ramp up the fitness factor with this difficult, yet doable Flat Belly Plank Challenge. It will mentally and physically challenge you, and, as an added bonus, leave you looking fierce. Now that's a full-body, inside and out-, fitness program we can all get behind.