How to do it: Sit on the ball, then roll out until your shoulders are on the ball, and your legs are at a 90-degree angle. Keep your hips and torso parallel to the ground. Interlock your hands straight up above you, then rotate your torso to the right until you roll up onto the side of your right shoulder. Return to the starting position. “You want to keep your hips parallel to the ground. They will deviate slightly, but try to keep them as parallel as possible,” Hiniker says.
Reps: 10 to 15 to each side
What it works: Inner and outer thighs, hip stabilizers, core, shoulders, back, posterior chain