10 Biggest Fitness Mistakes That Are Making You Fat

Mistake #3: You’re a crunching queen -- hey, it’s the way to get rock-hard abs.

Crunches alone will not give you a flat stomach. The fact is, if you want a killer core, you need to train all the abdominal muscles -- the rectus abdominus (muscles typically associated with a six-pack), the transverse (muscle that wraps around your stomach, acting much like a girdle to shrink your waist) and the obliques (muscles that run along the sides of your tummy and help with twisting motions) -- along with your lower back. These muscles all work together to provide stability and strength. A good way to hit them all is through functional movements like lifting, throwing, etc. But wait! There’s a part two to all of this: Building ab muscles isn't going to do you any good come bathing-suit season if they're hidden under a layer of fat. No matter how many sit-ups you do, without regular bouts of cardio (at least 20 minutes, four to five days a week) and a healthy diet, you're never going to sport a six-pack.