"Most core workouts are lacking in standing rotational exercises, which really does their results a disservice," McGee says. That's because rotational exercises, especially when performed standing, hone in on the internal and external obliques, which run along your sides forming the coveted "deep V," and are in charge of rotating your torso.

How to do it: Attach a handle to a cable station* (or firmly tie a resistance band to a sturdy object) about a foot above head level. Standing with your feet shoulder-width apart and one shoulder facing the station, grab the handle with both hands so that your arms are fully extended and diagonal from your body. Squeeze your abs to pull the handle diagonally down and across your body to the opposite thigh, turning your torso as you do so. Pause for one second, then slowly reverse the motion to return to the starting position. That's one rep. Do 10 reps, then repeat on the opposite side. Complete two to three sets per side.

*The cable station weight should be enough to allow you to just squeeze out your last rep with proper form.