Start lying face-up on a mat with your knees bent and your feet flat on the floor. Your heels should be about a foot away from your glutes.
From this position, lower both legs to the right side of your body. Your right leg should be touching the ground, and your left leg should be stacked on top of the right. Your upper back and shoulders should be flat on the mat.
With your hands behind your head or crossed in front of your chest, engage your core to slowly lift your shoulders and back off the ground, performing a crunch. Keep your neck long.
With control, lower your upper body back to the floor.
Repeat for 10 to 30 seconds on each side, then rest for a maximum of 30 seconds.