You may be familiar with bicycle crunches, but you can take them one step further. Watch Health‘s Contributing Yoga and Wellness Editor Kristin McGee demonstrate a Pilates version that involves even more rotation in your core.
Here's how to do it: Lie on your back and bend your knees into tabletop. Put your hands behind your head and lift your head and neck up. Take one elbow and cross it to the outside of the opposite knee as you twist and look over your back elbow. Do that motion on the other side. That's one rep; do 8 to 10 total.
Tip: Concentrate on keeping your shoulders up and away from the floor and the tops of your shoulders down and away from your ears.