Side Plank Raises
This works in an office setting because it's a quiet move and doesn't take up a lot of space, just the width of your body. Lie on your side propped up on your elbow, which should be directly under your shoulder. Stack your feet so they form a straight line with your body. Lift your hips off the ground, top hand on your hip for support. Hold for a count of three, and then lower back down. Do three sets of 10 reps per side.