Attach the chord to the lower part of a door or immobile object, lay down on the floor face up with your knees bent and feet flat, grab both handles and place both hands together above your face and keep your arms straight, curl your torso upward and focus on pushing your lower back into the floor while squeezing your abdominal muscles at the same time,then slowly lower to the floor.
Grab a dumbbell and lay flat on the floor (or an exercise ball) with your arms and weight across your chest. Slowly raise your upper body and do a crunch, getting a tight contraction Focus the tension on your abs and flex your stomach at the peak position.
Lie face up on the floor with your knees bent, holding a kettle bell in hand over your face. With the kettle-bell in position, contract your abs to raise your shoulders off the floor.
Place a bench in the middle of a Smith machine. Lie face up on the bench with your knees bent and feet flat on the bench. The bar should line up over your upper abs as you hold the bar at arms length above you with your back flat on the bench. Use your abs to explosively lift your torso up as high as you can, pushing the bar up as your body rises. Slowly lower your upper body back to the bench and repeat for reps. You can also do this exercise from the floor.
Lie faceup with your knees bent about 90 degrees and your feet flat on the ground. Hold a medicine ball at your chest with both hands. Contract your abs explosively to raise your upper body off the ground while at the same time extending your arms powerfully and releasing the ball at the top, throwing it to a partner. Get the ball back from the partner, then slowly lower back to the start position and repeat for reps.
Lie face up on the floor in the typical crunch position with your feet flat on the floor and legs bent. Keep your hands behind your head. Crunch up bringing your left elbow toward your left hip and return to the start. Next, crunch up bringing your left elbow toward your left knee and return to the start. Next, crunch up bringing your left elbow between your legs and return to the start. Next, crunch up bringing your left elbow towards your right knee. Next, crunch up bringing your left elbow towards your right hip. Then crunch up bringing your right elbow towards your right hip. Next, crunch up bringing your right elbow toward your right knee. Next, crunch up bringing your right elbow between your legs. Next, crunch up bringing your right elbow towards your left knee. Next, crunch up bringing your right elbow towards your left hip. That completes one rotation. Perform as many complete rotations as possible until reaching muscle failure.