Lie flat on your back with your hands behind your head and your knees bent.
Lift your feet off the ground and bring your right knee towards your chest while simultaneously twisting your torso to bring your left elbow towards your right knee.
Straighten your right leg while bringing your left knee towards your chest and twisting your torso to bring your right elbow towards your left knee.
Continue alternating the twisting motion, as if you are pedaling a bicycle, while keeping your core engaged throughout the movement.