How to do it: Lay on your side with the Swiss ball between your feet. Put your right arm directly beneath your shoulder and press up. Elevate your hips off of the ground, and point your left arm straight in the air. Reach underneath your body with your top arm to touch the ground, then bring the arm back up into the vertical position, squeezing your shoulder blades. Repeat on other side.
Note: If it’s too difficult to do this with your bottom arm extended, rest on your forearm instead of your hand. “If you’re falling backward,” Hiniker says, “You’re doing it right. It’s not dangerous, but hard.”
Reps: 10 on each side
What it works: Shoulders, core, obliques, quads, outer thighs, hip rotators, and your balance