Starting from a basic plank (you can choose whether to be on your hands or elbows), bend your right leg until the knee lightly taps the floor. Then, straighten the leg back to plank and repeat with the other leg. Repeat for one minute. Throughout this exercise try to keep the rest of your body as still as possible. "These are very small, isolated movements that require a lot of core, much like during sex," says Schmit. Other plank variations she recommends include bringing each knee to your chest, and planks where you touch your hand to your shoulder, extended it out in front, and then bring it back to start position.