The side-to-side crunch and weave builds strength in the midsection while also incorporating a cardio training component.
Stand with feet wider than hip-width apart, toes pointing outward, and hands in a fighting position directly in front of your face.
Maintaining a slight bend in the knees, quickly lean and crunch the body to the right and return to center.
Then lean to the left and return to center.
Finally, make a circular motion with your upper body by leaning to the right, moving across the center line of the body, and leaning back up towards the left side of your body.
Return to the starting position and repeat.
Avoid round your back. Instead, keep spine long and back flat.
Don't allow hips to wiggle. Keep them stationary and facing forward throughout the exercise. The movement should come from your midsection.