Put your hands behind your head and lie on your back. Stand up straight and bring your right arm up to your left knee. At the same time, stretch out your right leg and keep it off the ground.
Do a plank on your hands to start. Turn your hips to the right and bring them down toward the floor. Go back to where you started and do it again on the left side. During the whole process, keep your core tight.
Put your feet flat on the ground and bend your knees. Keep your back straight and lean back a little. Turn your torso to the right until it touches the ground next to you. Go back to the middle and do it again on the left side.
Lay on your back with your arms and legs stretched out. Keep your legs straight as you lift them up toward the ceiling. Bring them back down slowly so they don't touch the ground.
Start in a plank position with your shoulders back and your hands lined up under them. Bring your right knee up to your chest and quickly switch to your left knee. Keep up a fast pace and keep your core engaged the whole time.