The corkscrew exercise is performed lying on your back with your hands placed on the floor next to your hips or behind your head for a more challenging variation. From here, you’ll softly bend your ...

To work the lateral muscles while doing sit-ups, twist slightly to the left for five sit-ups, and then do the same thing to the right for five repetitions.

Optimal sets and reps: 3 to 4 sets of 15 to 30 reps As you come up in the traditional sit-up, twist your torso toward one side, bringing the opposite elbow toward the knee on the twisting side.

The main difference between sit-ups and crunches is the range of motion involved in each exercise. Sit-ups require you to lift all the way up, while crunches require a slight lift off the ground.