Dumbbell wood chop
The dumbbell wood chop is another excellent free-weight exercise that targets the entire core, requiring engagement of the deep stabilizing muscles of the abs and back while simultaneously hitting the obliques and rectus abdominis.
Stand with your feet roughly shoulder-width apart, holding a single dumbbell between your hands at your hips. Tighten your core, press your hips back, and squat down slightly as you rotate your torso to the right until the dumbbell is positioned just to the outside of your right thigh. Your arms should be straight -- they'll remain straight throughout the exercise.
In a controlled motion, sweep your arms diagonally up and across your body as you rotate your torso to the left and stand tall. At the top of the movement your arms should be extended above and to the left of your left shoulder. Reverse the movement and sweep your arms diagonally down and across your body as you rotate your core to the right, the dumbbell returning to its position just to the right of your right thigh.